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To put an animal, mainly rodents such as gerbils, rats, mice, etc. into one's anus, preferably with a safety cord, for sexual pleasure.
(Please note; This is most likely illegal and very painful. Don't do it. Please, for the love of all that is holy. Just think of the poor gerbils...on second thought, don't. Ever.)

John: Man, Jake put a snake up his ass, last night.
Jim: You mean he's runnelling?
by WolfJobOfficiando74 September 14, 2015
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