A combination of the words: crap and poop used when you are trying to tell somebody that you do not feel well. Coop is used when you are not bullshitting for the purpose of a) not going to school b) ditching the clingy girlfriend or c) any other circumstance where you might try to convey a false sense of illness. Coop is used when you feel so shitty that you cannot decide on whether you want to say that you feel like “crap” the more gentle “poop” and end up slurring the words together, into coop.
Dude#1: Yo man, wanna hit up the mall later??
Dude#2:....dude....i dont feel to hot...feel like...coop...
Dude#1: o man, sorry, you must really feel shitty, u cant even get your words strate!