WPU 

An acronym commonly used in many "AIM" screen names, yet no one knows the true meaning of it.

Juan: Hey! I heard you finally got a new screen name, your old one was lame... What is it?!

Sammy: Ohh yea, It's wpu6. I'm not sure why, but I like it! :D

WPU by Pseudomaster48 May 2, 2010

WPU 

Wish People Understand! Understand becomes Understood in Past tense! (more common)

Sarah tweeted: People need to believe that seatbelt is for their own safety! WPU!

WPU by ForeverSpn September 8, 2013