Expression: Faire (un) demi-tour
Pronunciation: [deu mee tour]
Meaning: to make/do a U-turn, an about-turn, an about-face
Literal translation: to make/do (a) half turn
Notes: The French phrase demi-tour can be used literally and figuratively, but the expressions are slightly different.
To talk about a literal U-turn, such as while driving, the expression is faire un demi-tour - note the indefinite article.
Je pense que nous avons loupé l'embranchement - il faut faire un demi-tour.
I think we missed the turn-off - we need to do a U-turn / we need to turn around.
To talk about a figurative U-turn, like when a person suddenly says the exact opposite of what s/he'd been saying, the French equivalent is faire demi-tour - with no article.
Martin se moquait de la coupe de Cristelle et puis, quand elle est arrivée, il a fait demi-tour en lui disant qu'il l'adorait.
Martin was making fun of Cristelle's haircut and then, when she arrived, he did an about-face and told her he loved it.