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?
John: Man, Jake put a snake up his ass, last night.
Jim: You mean he's runnelling?
by WolfJobOfficiando74 August 10, 2015
The last name of some of the baddest mofos you will ever come across. Also best at fishing and loving the ladies. The runnels family gives no fucks and are quick to put a good ol knot on your head if you get out of line. Especially one named Shane Runnels.
by Waterboi409 March 26, 2018
A term used to describe a less than attractive woman who may be up for a bit of action. A word play on "rough tunnel" to highlight the roughness that would be experienced while fucking her. The phrase originated amongst Australian rugby players in the 1980s and has since become popular in the UK.
by barely21 November 6, 2006