an ex-girlfriend who is now/still a fuckbuddy; an ex-girlfriend to whom you still make booty-calls.
John: Dude, did you just sleep with Jenny again? I thought you guys broke up last month?

Rob: Yeah, well, I still use her for booty-calls every now and then. She's a sex girlfriend.

John: I see...
by Driscool December 11, 2006
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A girl you relate to as if she's your girlfriend but you aren't having sex with. Can be a friend's girlfriend, a close friend, a roommate, etc. Often results in sex. Sometimes you deny each other sex since its immoral or taboo (c.f. friend's girlfriend "no sex girlfriend"). Other times it's just because one of you isn't into the other or it's mutually platonic but just kind of creepy how much you act like you're banging. Can be abbreviated using the acronym NSGF.
"Man, you should really watch out with her, you guys are acting like boyfriend and girlfriend"
"I know, she's my 'no sex girlfriend', wish we were doing it."
by secretuser420 February 21, 2018
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When a male normally around the age of a high schooler or college student; however cases have been found in other age groups, refuses to dumb an annoying bitch of a girlfriend once he starts having steady sex with a girl for fear of not being able to find someone else to fuck and suck his dick on the reg in an timely fashion.
Everyone - Bro, we hate your girlfriend. She is an annoying bitch let alone ugly and you could do a lot better.

Pussy whipped Guy - You do not know her like I do. She's really nice once you get to know her and I am not going to do any better.

Everyone else - Give it up Jeremy has Girlfriend Sex Syndrome (GFSS).
by Dr. Broberg October 17, 2010
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