Definition from Wiktionary, the free dictionary
cumslut (plural cumsluts)
- (slang, vulgar, usually derogatory) A person who badly wants to receive a man's semen, particularly in an orifice.
-  2001, ‘Teal_Guest’, quoted in Virtual Gender: Technology, Consumption and Identity Matters, Alison Adam and Eileen Green edd. 
- Teal_Guest: A pretty little cumslut, on her knees, dress tugged up over the lace of her stockings. She looks up at you and you can see that her face, dress and hair are streaked and spattered with cum.
2003, K S McCoy, My Mind’s Eye:
- He said girl in order to be worthy of being my cum slut my pleasure slave you will learn to love pain and take it.
- 2004, Patrick Califia, “Pussy Boy,”in Law of Desire: Tales of Gay Male Lust and Obsession, Ian Philips and Greg Wharton edd. 
- “Oh, Daddy,” he cried, his head rolling back over the edge of the sling, “[...] Oh Daddy, let me be your cum slut, I’m nothing but a hot pussy that needs your big load.”
- 2005, Ray Gordon, Depravicus: The Sequel 
- His penis twitching expectantly, he was sure that the little cumslut wouldn’t hesitate to lift her habit and impale herself on his magnificent penile shaft and fuck her tight pussy to orgasm. But he wasn’t so sure that she was a little cumslut. If she wasn’t, she soon would be.
-  2001, ‘Teal_Guest’, quoted in Virtual Gender: Technology, Consumption and Identity Matters, Alison Adam and Eileen Green edd.