Short for "coo," which is short for "cool." It is used as a positive acknowledgment or a signal of approval, not as an adjective.
Proper use:
"Hey, we're going to meet up with Jimmy at six."

Improper use:
"Get the fuck off my sister"
"Yo man, be co"

by d c a January 28, 2008
A shortened version of the adverb "coldly" used in hip hop culture which is often used merely as an extra syllable in hip hop lyrics and means "just" or "simply."
I was co shootin' some hoops before I went to co get ill.
by Andrew January 14, 2006
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!
by COSsayer March 30, 2011
When two or more people are going somewhere. You are not going, you are coing...
"Where will all you guys be tonight??"

"We are all coing to the movies."
by prinksmadge March 31, 2010
Wow, or cool.
Sounds like 'Koe'
'oh!' with a 'k' in front
"Dude that chick just fell!"

by luvbo April 5, 2008
Comfort Over Swag- Usually given to the guy who'd rather wear sweatpants than jeans out.
"John really believes in COS, dude."
"Yeah he was wearing sweatpants and a sweatshirt to the club last night."
by COS pro June 7, 2013
Abbreviation for "Chamber of Secrets", the second book on J.K. Rowling's Harry Potter.
by Raqueli88 September 4, 2006