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Taking a shit and/or diarreah on a girls' head and then rubbing the excrement-covered cranium on the floor like a broom.
Yo I totally gave Dereks' mom a Guntilda last night.

Aw shit Norma wanted a Gruntilda soo bad, but i gave her a piledriver instead.
by dfreshhh September 09, 2008
The evil witch from Banjo Kazooie and Banjo Tooie. Tries to kidnap Banjo's younger sister in Banjo Kazooie, and when foiled, comes back for revenge in Banjo Tooie.
"Run away! Gruntilda is coming baaaack!"
by alexanspaugh June 24, 2005