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1.
UBD
An acronym referring to Uncontrollable Boner Disease. Victims are subject to getting a boner from pretty much everything, including (but not limited to) head pats, colorful lights, the smell of delicious food, or watching tv.
Guy 1: "Hey man, why weren't you at Todd's party last weekend?"

Guy 2: "I was getting emergency surgery to treat my Type IV UBD."
by chunsberger October 03, 2011
 
2.
UBD
Often entered in technical support notes. Means User Brain Damage.
User stated that he smells something burning and he see's smoke coming from his computer tower. Also, he spilled his drink on it earlier. Could not assist customer further because of UBD.
by Benz0 November 14, 2004
 
3.
The surprise when you realised someone added a description of you on urban dictionary.
Woah, you've been ub'd!
by woahed November 10, 2010