Under-Bum 

An area located beneath the Buttocks, If ticklish it is open to the act of Under-Bumming, where a second party uses a hand to squeeze the area as a method of acute torture.

Usually not to extract information, But to extract uncontrollable laughter and strange noises from the Under-Bumee.

Person 1 : I'm bored, I'm going to Under-bum you!

Person 2 : NO! I cant take another Under-bumming!

Under-Bum by Thomasjeffy December 9, 2014

bum udder 

A man or woman can get these by eating too much of the wrong stuff........ You guessed it, piles. Doctors will suggest more fibre and fruit in your diet.

Simon "I can't sit down" Brad "you must have bum udders"

bum udder by RAWSTAN August 26, 2015

Under the bumper warranty 

When a woman gets that extra stitch in her hoo-ha after having a baby so that her mans slim jim will feel huge

Me: I bet that it’s like throwing a hotdog down a hallway.

Shane: No sir! She’s got that Under the bumper warranty. It’s tight.

Under the bumper warranty by Red Juan Elgordo February 17, 2024

UnderBum 

1. When a female wears really short shorts and reveals the underside of her ass to passers by.

2. God's gift to ass men.

3. Also known as ass cleavage.

Adam: holy shit that chicks ass is hanging out! I think my dick just moved.

Craig: That my friend is some grade A UnderBum.

UnderBum by Hector the molester July 28, 2010

Underbum 

When a female has a second bum

almost like a double chin

"does my underbum look big in this?"

"does this skirt emphasize my underbum?

"underbum is way rank"

Underbum by Chickenpastababy October 13, 2011