When someone is blowing you in a pool and you are walking backwards "towing" them around the shallow end with your knob while making motorboat noises. A variation would be the steamboat, this would be done in a hot tub instead.
I am banned from the public swimming pool for life after doing the tow boat in front of all of those families with that lifeguard last month.
by Special needs student November 25, 2010
A self-propelled vessel which moves other, usually non-self-propelled vessels. May be in the form of a pushboat, a square- or flat-bow boat designed to rigidly connect to a barge or barges for the purpose of pushing it or them along a waterway. Not quite the same as a tugboat, which usually assists ships.
by Wandelndes Lexikon January 05, 2005