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1.
Slang for the headcrabs in Half Life 1 and Half Life 2.
Headcrabs latch onto the victims head and turn him/her into a zombie, hence the name headhumper
"Look out, headhumpers!"
by lawzer February 07, 2005
 
2.
Headhumper is another word for the famous Half Life's Headcrabs.
"Get that figgin head humper off o me!"
by Adam Sklar April 04, 2009
 
3.
those things in mario bros. in the ocean that hump ur head.....
the headhumpers are coming! swim! swim!
by kim January 20, 2004