Similar to a turtle head, a boat knob is a small piece of poo, that has emerged from the anus, while the rest of said poo is still submerged inside the rectum.
Bogan 1: Oi where's the dunny cunt I got a boat knob hangin out.
Bogan 2: Down the hall and to the right you filthy cunt.
Bogan 2: Down the hall and to the right you filthy cunt.
by Crumbed Cutlets March 31, 2016
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