underfuckingstand 

When you don't understand something and you are super pissed.
When you don't feel like saying "fucking understand"
When fucking understand just doesn't quite display the needed emotion.

"I don't underfuckingstand why your acting like this"

underfuckingstand by Desiree Aho January 9, 2008

underfuckingstand 

underfuckingstand - Understand, with "Fucking" inserted in the middle, making it an exclamation of frustration or, in some cases, a joking statement.

"What part of this do you not underfuckingstand?!?" or "I dont underfuckingstand!"

underfuckingstand by Steve October 24, 2004

Underfuckingstand 

When you don't understand something but you're angry

Tecate can't underfuckingstand this game.

Underfuckingstand by raymondamantius August 15, 2019