Undersplain 

Understand and Explain conjoined together as one word.

"It's hard to undersplain"

Undersplain by silly_duckee May 24, 2009

Can't Undersplain 

The inability to understand or explain something. Usually while chemically augmented AKA fucked up.

Hey bro I'm walking around Electric forest and I can't Undersplain an effin thing soooooo gonzo

Can't Undersplain by Benjiblueyes April 13, 2020

Understains 

A name given by 1970s UK washing powder manufacturers for stains that won't wash out. A polite word for shit or bodily fluids of some sort on underwear.

"Has your washing got understains you can't remove"? "Use new Daz powder to remove them fast"!

Understains by prof_evil May 14, 2011

Undersplash 

The outcome of downward force of female urine, splashing back up to the underneath of the toilet seat

She was responsible for undersplash when seated on the toilet

Undersplash by Bvs1 June 12, 2022