Isobutyl

The 4 carbon branch that looks like a penis with a line of 3 carbon atoms with hydrogens all around 'em and one attached to the central of the line.

Dude1: Hah, your penis is smaller than an isobutyl

Dude2: You don't even know what a hydrocarbon chain is, you just read the Urban Dictionary definition

Dude1: No u

by Ugo Flickerman December 20, 2018