Top Definition
(noun)

An unwanted erection provoked by engine vibration on a bus or coach.

A debilitating condition afflicting mostly, but not exclusively teenage boys.
- "Press the bell, it's our stop next!"

"Oh fuck I can't stand up yet, I've got Coachman's knob. you'll have to wait. Sorry nan."
by JingJangJong April 21, 2012

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