Il n’a pas sourcillé.
eel nah pah soor-see-YAY. Click below to hear this.*
He didn’t bat an eyelash.
Actually, in French, it’s a whole eyebrow. It’s hard to bat just one eyelash, anyway, and eyebrows don’t “bat”.
Un cil (/seel/) is an eyelash. Un sourcil (/soor-SEE/, without pronouncing the l–don’t ask me why) is an eyebrow. That sour- is an old form of sur, on or above, from the Latin super.
So sourciller appears to mean simply to do something with the eyebrows. Eyebrows don’t do much, anyway. They go up, down, and in towards your nose. This word generally refers to raising eyebrows.
But if you are playing poker or being interrogated by the police or trying to tell your teacher the dog ate your homework, you don’t want your eyebrows to twitch, not even a tiny little bit, not in any direction. If you succeed, we will get to say Il/Elle n’a pas sourcillé about you. Impressive trick.
*Some mobile phones, such as Blackberries, won’t display the audio player. If no player appears, here’s an alternative link to the audio file: