Overview
Compared to English-speaking folks, the French use very little religious-based swearing (again, things are quite different in Canada). Not because it's taboo, quite the opposite: religious swearing has pretty much lost its bite, and now sounds a bit quaint. Mon Dieu, doux Jésus (= "my God, sweet Jesus") are things your grandma could say. Amusingly, when I hear teens speaking, I think they use the English oh my God more often than the native oh mon Dieu. The only ones that are still in somewhat frequent use are bon Dieu (good God) and nom de Dieu (name of God).
So, the French will usually swear by bodily functions, and sex-related words. Luckily, there is a plethora of those to choose from.
A word about gender: as is usual in Romance languages, adjectives and nouns can have both a masculine and a feminine form. For swear words, it's common for the feminine forms to have fairly different connotations from the masculine ones.
Con/conne
A general-purpose insult: it can mean "asshole" or "moron". Originally it meant female genitalia (it's a cognate of "cunt"), but this use sounds quite dated now. Due to overuse, it's now less offensive than it used to be, but still considered a swear word.
This word can be used as a noun: bande de cons, c'est un con (a bunch of morons, he's an asshole); it's also an adjective: il est un peu con, c'est vraiment con (he's a bit stupid, this is fucking stupid). The feminine forme is normally conne: elle est vraiment conne, mais quelle conne. Lately though, I've been hearing con as an adjective even for females, such as elle est un peu con.
Quel con ! can be used as an insult, or to underline your own stupidity ("what an idiot I've been!").
Another variant: à la con, to describe an object or an activity. Un jeu à la con = "a silly game". Une émission à la con = "a shitty TV program".
Derived words:
- connard/connasse: a stronger variant, very similar to "bastard" (i.e. it means the recipient is a jerk rather than stupid).
- connerie: bullshit. Faire une connerie: to do something very stupid. La connerie humaine: human stupidity. Dire des conneries: to talk rubbish, to bullshit.
- déconner: to do or say very stupid things. Arrête de déconner: stop fooling around, stop kidding me. Mais non, je déconne: I'm only kidding, I'm being silly. My personal catchphrase is Faut pas que déconner.
One of those words that has very different connotations depending on gender. The masculine form salaud means "asshole, bastard".Quel salaud = "what a bastard". Cet enfant de salaud = "this son of a bitch".
On the other hand, the feminine form salope is closer to "slut", meaning sexually depraved. As a result, it is quite stronger than its male counterpart. (You could draw parallels with "bastard/bitch" in English).
- saloperie: something dirty. Laisse pas traîner ces saloperies: don't leave this bullshit around. Choper une saloperie: to catch a disease (especially an STD).
- saloper: to make a mess. Elle a salopé mon boulot: she screwed up my word.
Quite simply "shit", either litterally or not: c'est quoi cette merde ? = "what's this shit?", être dans la merde = "to be in deep shit". Very popular as an expletive: Meeeerrde !!! = "Shiiiiiiiiiittt!!!". Variants: Oh merde, merde alors.
You can follow a noun with de merde: un film de merde = "a shitty movie".
There is a superstition that saying bonne chance (good luck) actually brings bad luck, so people sometimes say merde to wish good luck to someone (think "break a leg" in English).
- merdier: a bloody mess.
- emmerder: to bother someone, or to bore someone. Ce type m'emmerde = "this guy's a pain in the ass". Un livre emmerdant = "a fucking boring book". (Variant: emmerdifiant). Added by request: Je t'emmerde = "screw you".
- merdique: shitty.
- se démerder: to get oneself out of trouble. Démerde-toi: deal with it on your own. Famous comedian Coluche joked that he wanted to have as an epitaph Et maintenant, démerdez-vous "And now, deal with this shit by yourselves".
Literally "to shit". Je vais chier = "I'm gonna take a dump". Often used in the figurative sense. Faire chier: to annoy, to bore. Fait chier!, a generic expletive. Chiant: very boring, or annoying.
Cul
"Arse, buttocks". The L is silent: /ky/ (exactly like the letter Q, which amuses grade-school pupils to no end). It's used pretty much exactly like the English "ass", so no problem here. Un joli petit cul: "a nice piece of ass"; botter le cul à quelqu'un: "to kick someone's ass". Do not mix up merci beaucoup "thank you very much" and merci beau cul "thank you, nice ass".
The word can be used to refer to sex in general. Un film de cul = "a porn film". Une histoire de cul = either "an affair" or "a dirty joke". Un plan cul = "a booty call". Blagues de cul = "dick jokes".
Derived expressions:
- cul-de-sac: dead-end. cul-de-bouteille: bottom of a bottle. Bizarrely not considered vulgar despite their origin.
- avoir du cul: to be a lucky bastard. Variant: avoir le cul bordé de nouilles (litterally "to have one's ass covered with noodles". No, it doesn't make any sense.)
- enculer: to bugger, to sodomize. Can be in the figurative sense. Je me suis fait enculer par les impôts = "I got screwed by the taxes".
- enculé: a very strong insult. Because of its homophobic connotations, this one has become somewhat taboo in recent times.
By far the most common slang word for testicles: "balls, bollocks". It's grammatically a feminine word, which makes absolutely no sense whatsoever: what could be more quintessentially masculine than a pair of bollocks?? (No offence to transwomen, I mean.) Un coup de pied dans les couilles: a kick in the nuts.
- Casser les couilles: to get on someone's nerves. ça me casse les couilles, this pisses me off (this one is used even by females).
- Je m'en bats les couilles: I don't give a fuck. Again, even females use this one.
- avoir des couilles: to have balls. T'as pas les couilles de faire ça: you don't have the balls to do that. Variant: avoir des couilles au cul (litt. "to have ball up one's ass". Someone said about Maréchal Lyautey, a courageous military leader rumored to be gay, that Il a des couilles au cul, même si ce ne sont pas toujours les siennes: he had balls up his ass, even if they aren't always his.)
- partir en couille: to go completely wrong, to go apeshit.
- il y a une couille dans le potage: there's a hitch somewhere.
Originally "she-cat", it means the female genitalia; just like the English word "pussy". I'd say it's a bit more offensive than "pussy", but not as much as "cunt".
Other words for the same body part: minou (also from cats, this one is more childish), moule (litt. "mussel").
Bite
"Cock, dick". Very common. It's a feminine word (which, again, is completely absurd, but hey).
Synonyms: zizi, noeud, teub, zguègue, zboub.
Nichons
"Boobs, tits". A masculine word (ditto). Other words: nénés, doudounes, loches...
Pute
Quite simply "whore": originally a prostitute, by extention a promiscuous woman. Nothing much to add here.
- faire la pute: to whore oneself out.
- un coup de pute: a low blow, a dirty trick.
- fils de pute: son of a bitch. Also sa mère la pute: motherfucker.
- putassier: overly commercial. Leur dernier album est vraiment putassier: their latest record is really a sellout.
An etymological doublet of the previous one; but it has taken a life of its own, and now rarely refers to an actual woman. Mostly, it's used as a general expletive, comparable to the English "fuck".
Actually, it's the closest rival to "fuck" in terms of syntactic versatility: un putain de bon film, a fucking good movie; on s'est putain de planté, we done fucked up; un putain de salaud, a fucking asshole.
Bordel
Originally a brothel or bordello, it can be used to mean "a fucking mess": C'est quoi ce bordel ?, what's this racket? Foutre le bordel, to make a bloody mess. It is also used as a general expletive, Bordel !.
Baiser
As a verb, it means "to fuck, to screw". Ils ont baisé comme des bêtes = "they fucked like rabbits". J'ai pas baisé depuis des mois = "I haven't had any in months". On s'est fait baiser = "we got screwed".
It's tricky, because as a noun, un baiser means a kiss, and is perfectly innocent. In older works, you can still find the verb baiser meaning "to kiss", which makes modern readers blink twice (think when you read that a character "ejaculates" in 19th century novels). Today, "to kiss" is embrasser.
There are lots of synonyms: niquer, tirer un coup, sauter... Nique ta mère = literally "screw your mom", or loosely "motherfucker" (very common in rap music).
Foutre
A tricky one. It's an irregular verb, and its meaning varies widely depending on syntax.
As a transitive verb, it's a vulgar way to say "to put". T'as foutu de la peinture partout: you've spilled paint everywhere. Où j'ai foutu mes clés ?: where the hell did I put my keys?
As a reflexive verb, it means "not to care". Je m'en fous: I don't care. Je me fous de sa vie: I don't care about this guy. A stronger form: Je n'en ai rien à foutre = "I don't give a damn". (Though Rhett Butler's line was bowdlerized to c'est le cadet de mes soucis, that's the least of my concerns.)
As an adjective, foutu means "broken, spent". Je suis foutu: depending on context, it can mean "I'm spent" or "I'm screwed". C'est foutu: "it's done, it's doomed". Sa voiture est foutue = "his car is FUBAR".
As a noun, du foutre means "semen".
Added by request: Va te faire foutre means "fuck off, go fuck yourself".
Branler
As a reflexive verb, se branler means "to wank, to jerk off".
When not used reflexively, it can mean "to be lazy". Qu'est-ce que tu branles ?: what the fuck are you doing? (with the implication that you're beating around the bush and should be doing something else right now.) J'en ai rien à branler is similar to rien à foutre as seen above: "I don't give a flying fuck".
Un branleur means a lazy person; "wanker" in the UK is actually very similar.
Espèce de
Not a swear word by itself, but a frequent addition: when saying an insult to someone, you can add espèce de in front of it. It works with Espèce de connard, espèce d'enfoiré = "you bastard".
Note that there's no direct equivalent to the English practice of adding "You" in front of an insult, so espèce de sort of works as a loose equivalent.
Cuss words chaining
As anyone who watched The Matrix Reloaded should know (just in case: https://www.youtube.com/watch?v=HfnmkgmUDW4), the French love to strings insults together. Just use any cuss words, linked together by de, trying not to repeat yourself (or, for effect, repeat the same one thrice in a row). Pay no attention to meaning, or even lexical categories: just keep going, until you either run out of breath, out of words, or feel that you have vented enough. Putain is a good starter; ta mère (your mom) is a nice ending point.
Putain de merde and bordel de merde are particularly common (I've seen BDM online as an acronym for the latter).
A sample, off the top of my head:
- Putain de bordel de poil de cul d'enfoiré de fait chier de sa race.
- Bordel de fait chier de fait chier de fait chier de ta mère.