Fais gaffe

Expression: Fais gaffe !

Pronunciation: [feh gahf]

Meaning: Be careful! Watch out!

Literal translation: Make mistake!

Register: informal

Notes: The French expression fais gaffe is interesting because it means just the opposite of its literal translation. Faire une gaffe means "to make a mistake, to blunder," so you would think that "be careful!" would be something more like ne fais pas de gaffe ! Apparently leaving out une is enough to turn the meaning around.

You can also say Fais gaffe à toi to mean "Watch yourself."

Example
   Ça peut être dangereux - fais gaffe !
   That can be dangerous - be careful!

More: Expressions with faire | Most common French phrases