underjawn 

Everything from the asshole to the front butt (male/female/shemale inclusive)
(see main entry for jawn)

Man, I could totally see her underjawn up her skirt!

or

My underjawn is all chafed and sweaty from riding my bike all day.

underjawn by Hogs of the Forsaken July 3, 2008

Wailing underpants

Activities in the underwear that demand immediate attention either sexual or toilet related.

Palmer had to go to the toilet quickly due to his wailing underpants!

Wailing underpants by I, Wreckerrr October 30, 2016

Underpants journalist 

A journalist who writes about and/or dressed in their underpants. Often referring to bloggers or freelancers who work from home/their parents' basement.

"TMZ may have broken the 'Michael Jackson is dead' story, but they're still a bunch of underpants journalists."

Underpants journalist by Stable of Crayons July 21, 2009

Underpants Gnomes 

From the TV show South Park. They steal underpants in order to make profit. They even educate children on how profit works. Here's how:
Stage One: Steal Underpants
Stage Two: ???????
Stage Three: Profit!

The underpants gnomes robbed my house again.

Underpants Gnomes by funwillfunwill June 20, 2015

Underpants Gnome 

A gnome who steals your underpants while you sleep.

Robert Farmery

Underpants Gnome by Ad May 17, 2004

underpants toss

Disposal method when one has sharted in a public place or at the home of friends or family. At work it is best to remove shorts, clean ass, and leave shorts on the coat hook in the stall for someone else to find. If visiting friends or family, it is best to be discrete and leave shorts in the bathroom trash can and cover with clean TP and tell no one.

I thought it was just a fart but ended up excusing myself from the dinner table to wipe up and had to do the underpants toss.

underpants toss by Bugsy McDingle December 7, 2012

Captain Underpants 

Greatest superhero ever. Created by Dav Pilkey.

Captain Underpants says "Tra la laaaaa!

Captain Underpants by Xarionis aka Omnivore December 13, 2003