Tune, thune (f)

= Argent (m)
= Money
NB: can be spelled with or without the "h"
Synonyms: All the other words in the "Money" category

"Il m'a prêté de la thune"
= "He lent me some money"

Mater

= Regarder
= To watch, to check out

"On a maté un film hier soir"
= "We watched a movie yesterday"

"Il aime mater les filles en été"
= "He likes to check out girls in the summer"

(There's a third meaning too, feel free to add examples of it in the comments!)

Enfoiré(e)** (m/f)

IMAGE: Couple yelling face to face (John Rensten / Corbis)

= Personne stupide, méchante, idiote
= Jerk, fucker
Synonyms: Con(ne)

"Espèce d'enfoiré** !"
= "You son of a bitch!"

Vitéf

IMAGE: A running clock with a face on it (Images.com/Corbis)

= Vite fait
= Quickly done, doesn't require much effort

"Tu ajoutes juste un petit texte ici, c'est vitéf, et puis c'est prêt"
= "Just add a little texte here, shouldn't take long, and then it's done"

Con(ne) ** (m/f)

IMAGE: Woman tossing popcorn at her date (Daniel Koebe/Corbis)

= Personne stupide, idiote
= Jerk
Synonyms: Enfoiré(e)

"Il m'a pas appelé hier, quel con** !"
= "The jerk never called last night!"

Faire gaffe

IMAGE: Exclamation point road sign (Robert Essel/ NYC/CORBIS)

= Faire attention
= Look out, be careful, watch out

"Fais gaffe à la voiture !"
= "Look out for the car!"

Chaud(e)

IMAGE: Man is standing in front of a white board (Wolfsteiner  / Corbis)

= Difficile
= Hard

"Les exercices de maths sont super chauds !"
= "The math exercises are really hard!"