1. slang To fall asleep. He was so tired after his long day at work that he conked off during the movie.
2. slang Of a machine, to break or completely lose functionality. Judging by all that noise coming from her car, I'm pretty sure it's about to conk off. The blender stopped working again today—it must be ready to conk off.
conk offand conk out
1. Sl. (from years ago.) to fall asleep. I conked off about midnight. I was so tired that I nearly conked off. I was afraid I would conk out while I was driving.
2. Sl. (always conk out.) [for something] to break down; to quit running. My car conked out finally. I hope my computer doesn't conk out.
in. to fall asleep. I conked off about midnight.