flat on one’s ass
flat on (one's) ass
rude slang On one's buttocks. Usually used to describe one's resting position after a fall. Oh, those steps were a sheet of ice—I fell flat on my ass!
(flat) on one’s ass
1. mod. completely exhausted. (Usually objectionable.) I’m just flat on my ass. I need some rest.
2. mod. broke; financially destroyed. (Usually objectionable. An elaboration of flat broke.) Sorry, I can’t help you. I’m broke—flat on my ass.