Definitions by Fuse fan

flench 

The simultaneous facial and sphincter clench just before a fart is released. 'Flench' is therefore a fusing of the key words 'fart' and 'clench'.

Mary: "My goodness can you smell that? Who farted?"
Joe: "It was Mark, I saw him flench right before the smell hit"

flench by Fuse fan February 26, 2010