Why do I need to know arriver comme un cheveu sur la soupe?

Because you certainly don’t want to be the one to arrive like a cheveu sur la soupe.

What does it mean?

Arriver comme un cheveu sur la soupe translates literally to “arriving like a hair on the soup”, which does not tell us a lot, a part from the fact that it’s quite gross.

According to French dictionary website L’Internaute, this expression stands for “arriving in a way that is incongruous, unadapted to the situation.”

So don’t be surprised if someone uses this expression while not eating, because it actually has nothing to do with a real soup but rather with someone (or something) who’s turning up at a bad, or unexpected time.

If you are having an argument with your partner at home and suddenly a friend arrives unannounced, you could think he just appeared like a cheveu sur la soupe because you were not expecting him and just like a real hair in your soup, it’s something you don’t really appreciate.

The expression can also be used to point at something (or someone) that's irrelevant. In a meeting at work, you may then hear ta remarque est arrivée comme un cheveu sur la soupe, meaning “your comment was completely irrelevant.”

Use it like this

J’étais en train de préparer le gâteau d’anniversaire de Pierre quand il est arrivé comme un cheveu sur la soupe – I was baking Pierre’s birthday cake when he showed up unannounced, his timing could not have been worse.

Sa réponse à notre question est arrivée comme un cheveu sur la soupe – His answer to our question was completely irrelevant.

Je n’ai pas aimé la fin du film, la mort du personnage principal est arrivée comme un cheveu sur la soupe  – I did not like the movie’s ending, the main character's death came out of nowhere.

Synonyms

Arriver à un moment inopportun – To arrive at an inappropriate time

Arriver comme un chien dans un jeu de quilles – someone’s who’s unexpected and who, therefore, is badly received