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2.
n. A girl who is always at the cock.
v. A person fucks like a fiend.
adj. Some who is too ugly to fuck
n. Damn Mo is such a fuck monster, she always grabing at my shit.

v. I tried to stay with it all night, but she was a fuck monster and I dried out.

adj. Look at Felix, he knows she aint looking at him, he's a fuck monster.
by P. Will November 04, 2006
 
1.
A phrase almost exclusively used by men talking about women.
A girlfriend with an absurdly high sex-drive, which initally seems great, but then you realise it's far higher than yours and you can barely keep-up, you can't sleep, you've no energy, you feel like death and STILL SHE WANTS MORE
James was overjoyed with his new girlfriend, but soon found-out that she was a fuckmonster.
by Andy WRX July 25, 2008
 
3.
A relationship definition somewhere between "friend-with-benefits" and "disease trader."
Ro Bag: "I'm not Katy's boyfriend, I'm just her Fuckmonster!"
by Marcus Chizzle December 06, 2005
 
4.
One who frequently engages in carefree sportfucking without regard to commitment, reason, or partners' emotions.
Yulia: William is a dirty, dirty fuckmonster.
William: You know you love it.
by Dino February 10, 2005