undie grundie 

The act of inserting a finger or thumb into an unsuspecting victims anus through their fresh new underwear, thus causing a permanent poo stain. If done in a forceful manner, blood stains may accompany the poo stains.

Paul surprised Steve with an undie grundie...a large fight insued.

undie grundie by Mutato January 30, 2008

Undie Varmint

A slang for either gender's genitalia.

" I sure would like to tame your Undie Varmint"

Undie Varmint by Drewdad71 July 22, 2020

undie punch 

to be reamed unknowingly, usualy from behind while still wearing ones underwear. resulting in undies being stuffed into the oriface in question

i gave that bitch from starbucks a rightious undie punch..
she was all like

"AWWWWWW i say stop that young man dont punch my underwear into my date"

"captain to the bridge, there has been a royal undie punching on the lower deck"

undie punch by reg the great October 16, 2007

Undie nuggie 

Poo in your underwear

When you leave a poo nugget in your undies. ‘You’ve got a undie nuggie mate ‘

Undie nuggie by Ramrodthinks May 7, 2021

undie punching 

To punch someone in the undies. With your penis usually.

Me: How was your date last simo? Any undie punching?
Simo: Hell yeah, was awesome too. Plenty of undie punching to be had.

undie punching by Rodney Stewart March 12, 2008

undie pumper 

People who engage in sexual practice fully or partly clothed.

I have a mate who enjoys being a undie pumper.

undie pumper by @Riflerangehoney April 10, 2017

Undie Stew 

A load of laundry containing only boxers and/or briefs.

Matt: "Hey Ed, want to go get a beer?"
Ed: "Can't right now. I am in the middle of brewing a fresh batch of undie stew. Maybe later."

Undie Stew by Latino Caliente September 11, 2010