Definition

Gum that's been accidentally sat on in your back pocket for too long, resulting in a melted, mushy, disgusting mess. A cautionary tale about pants pocket storage and personal hygiene.

Example Usage

I offered him a piece of gum, but it was clearly butt-gum from the mixer last weekend, so he rightfully declined.

Source: Urban Dictionary (https://www.urbandictionary.com/define.php?term=Butt-Gum&defid=3715200)