A combination of pubic hair and cotton lint, that becomes intertwined after swamp-butt and walking create optimum conditions.

Not like a dingle berry, whose main component is fecal matter, crusted onto pubic hair(s).

(see dingle berry )
I usually find 2 or 3 tumble bugs in my underpants by the end of the day.
by redrocket84 April 19, 2011
Get the tumble bug mug.
Let's ride the tango train! No, let's ride the tumble bug!
by Brooke hayes 4ever21 July 31, 2016
Get the tumble bug mug.