Acronym for Crab On Booty Syndrome. This syndrome occurs most often in high school and college students who haven't slept or gotten what they want over an extended period of time. Symptoms include irritability, hunger, the inability to co-operate with others, pouting, whining, frowning (in this case we will refer to it as an upside down smile), and a general distaste for the other people who inhabit planet earth.
"Damn she looks constipated, she must have C.O.B.S."
"Jesus! What is his/her problem? Maybe they would be in a better mood if that crab let go of their ass!"