A penis. Usually used to describe a penis that is used in questionable activities, such as 'rubbing it in' with an underage girl, or or all male group masturbation.
"I've got a ruler! Get your rub dogs, men!"
"I had this 16 year old girl petting my rub dog on saturday."
"I had this 16 year old girl petting my rub dog on saturday."
by Ωren October 8, 2008
by wolfbait51 June 11, 2011