Derived from the word wallop, which is onomatopoeia (a sound word) for an impact of some sort, it is a Scottish slang term for a penis, usually a large penis.
It is also used to refer to unpleasant people, much like dick, cock, prick and knob would be used in conversation.
"Jesus Christ, did ye see the size of that walloper he had on him?"
or
"He's a bleedin' walloper, and that's all there is to it!'
a really pretty girl who dosnt dance at parties. they hold up the wall. and laugh at other people dancing, and does anything to avoid dancing like eating, not that they cant but they won't.
-HEY (BOY)
-yo (LEEHA)
-come over here and dance with me (boy)
-nah i'm straight! (leeha)
-Leeha you are such walflower!