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a person that kills all fun/shits and giggles. boring not interesting person or annoying people.
"Don't talk to those kill fucks, they are boring as hell"

"watch out the kill fucks are coming"
by shits&giggles November 25, 2009
to engage in sexual intercourse with until victim, I mean, partner has stopped struggling
"I done killfucked da shiznit out o dat hizzo!"
by tug July 10, 2003