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1.
The act of taking a jizz on a woman's ass while she's still wearing her pants. The result of the man's unwillingness to wait for sex with his old lady creates a white stain on the woman's pants that is extremely difficult to get rid of.
Jerk #1 - "Yo brotha, there's a white stain on the back of your girlfriend's pants."

Jerk #2 - "I know. Last night I was so anxious to have sex with her, but I ended up giving her a cum bum instead."

Jerk #1 - "Word."
by Elmer April 09, 2005
 
2.
Where the anus is full to the brim with cum!
I aint going near that cumbum its spilling out everywhere!!!!
by Dave&Rich May 30, 2005
 
3.
"Cum Bum" or "Cum Bumming is a phrase commonly used in highly populated areas such as New York or San Diego. To "Cum Bum" is the act of which a male will masturbate and ejaculate on another male who is considered homeless. Thus "Cumming on a bum."

Cum Bumming originated in South Texas when an influx of Mexican Immigrants had crossed the border. Most of which became homeless. This event had aggravated local Texans and caused them to create ways to drive the Mexicans back. Killing and raping was popular but "Cum Bumming" became loved among most males 17 to 25.
Man 1: Dude, check out this fucking hobo Mexican. He's fucking asleep and everything.

Man 2: Dude! Fucking Cum Bum him!

Man 1: Hell yeah!
by BiGoDeViN28 December 22, 2012
 
4.
a person that likes to take it up the bum
Ashley is a cum bum.
by bumbumbum69 November 12, 2010
 
5.
An embarrassing bum cyst between the ass cheeks.
When popped, it resembles a river of cum flowing to Brown town.

1) "Cum Bum" said like an angry old man shouting at a young kid, Cummm Bummm!!!!
by Mr Cornhole October 11, 2011
 
6.
when you got semen between ur butt cheeks.
"me and sally were doin the doggy. and then i skeeted on her" says jose.

" oh no way dude you gave her a cum bum!" - javier

"yeah i did!" - jose

by jay doshi1 February 08, 2009
 
7.
A guy who has the back of his tousers covered in either cum or a cum looking substance. He decides not to change his trousers for ages and looks like a tramp to everyone.
Ewww! Cumbum change your trousers mate. youve had those on for 4 months now!
by spunklover123 February 23, 2009