look up any word, like spook:
 
1.
A mythological being based on the concept that there are women out there that are not bloodsucking, money-grubbing whores.
I thought Kelly was a cool girl but then I saw her suck dick for coke.
by Haywood J. Blohme October 18, 2009
 
2.
A girl who is not a girlfriend. Shares interests with, hangs with, and (optionally) sleeps with a man she is interested in. Inevitably, she becomes a 'cool girl' and becomes ineligible for girlfriend status. Is often beleived to be lesbian on first glance.
Guy 1: Sam likes Halo? You serious? Damn, you're lucky to have a girlfriend like that.
Guy 2: She's not my girlfriend. She's just a cool girl.
by Kathleen Henry May 11, 2006
 
3.
A pointless name catty girls will call themselves because they think they're better than everyone else.
"Carly is such a lowlife, but she calls herself a 'coolgirl'"
by heythereyoux3 April 08, 2009