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1.
when the male ejaculates in the vagina and continues thrusting to finish off the female causing ejaculate to leak out into her gluteal cleft
Dave ejaculated prematurely into Laura and he kept pumping and juice started coming out causing Laura to have a very cummy cum butt.
by ivana fuckalot February 10, 2008
 
2.
a pool of boy juices in a male or female anal cavity.
Sally Suckalot received a large cum butt during her porn adventures.
by JJOJJOJJO February 24, 2009
 
3.
Cumbutt is the sticky side effect of the male penis being removed rapidly post ejaculation. If the penis is promptly removed after male ejaculation, and is unprotected, semen will naturally run down from the vagina towards the anus;thus causing so called "Cumbutt".
Male and female in missionary position. Impatient male pulls out, and after ejaculation has his freshly ejaculated semen begin flowing into the females butt cheeks. Female responds "babe, you gave me Cumbutt"

Female-"Sweetheart my ass cheeks are sticky now!"
Male-"Ha, you got cumbutt."
by Wierdfeet987654321 August 08, 2011
 
4.
A word that means "Retard"
Did you Hear about that guy who said Daft Punk is gay?

Yeah. He is such a cumbutt!
by DaftPunk64 May 26, 2011