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 December 21, 2015
by Windwing March 10, 2016
by Hazertron12 December 18, 2015