abbrev. for Chill Out Slut; used when firing out the word "slut" is inappropriate, i.e. in a grocery store, courthouse, workplace, in front of children, etc. Encouragement for someone to relax, settle down, get out of your way, shut the hell up, etc.
Crazy bitch: "Did you hear about this and that and the other thing and this other thing and that person and what she did and he said and about what color underwear I'm wearing and what kind of weave do you have and where did you get that purse and did I tell you...."
Me: "OMG! COS! Seriously!