1.When someone goes to the toilet under the pretenses of taking a shit, but instead has a wank.
2.When someone goes to the toilet for a shit, and has wank while they're there.
"Okay, see ya guys, I'm going for a tugboat"
"My shit turned into a tugboat"
Tugboating - Similar to guiding a large ship into port, tugboating is the act of escorting a drunk friend out of a bar by having two people on each arm to insure they don't fall flat on their face.
Everything was fine at Mary's birthday party until they started doing shots. By the time they were done my buddy was so drunk we had to tugboat him out of the bar then into a cab to take him home.
when a man inserts his penis into a pair of buttcheeks, then the person twerks onto the penis until ejaculation occurs if the tugger is well versed in the motion of a tugboat