a cum stamp is possible only if the male has cum left over on his member then proceeds to slap his penis on a woman's face leaving cum residue wherever he slapped her.
Male 1: "Man what should I do with all this cum on my dick?"
Female 1: "Just wipe it off with a tissue."
Male 2: "Shut up bitch. Yo man give that bitch a cum stamp."
When a person gets cummed on and then presses their body onto a sheet, person, pillow, etc. leaving a perfect stamp.
"My boyfriend came on my stomach again last night, so I totally cum-stamped his pillow"
"Yo man, sorry about the cum-stamp on the shirt you lent me. You know how girls like to cuddle."
The act of cumming on a girls lower back where the "tramp stamp" is. This will render said "tramp stamp" illegible.
yo dude i totally railed that bitch from behind last night and turned her tramp stamp into a cum stamp