wtf

Generally stands for 'What the fuck'. Most people use a question mark afterwards to get the point through. Rather than using the same term for the other 'w's, who, when, where, and why, it makes more sense to actually state the word and follow it with 'tf'

Capitalization doesn't really matter.
This term can also be likened to 'What the shit?' which is more comical and has a tantamount meaning.

The World Taekwondo Federation.
WTF, holds many competitions throughout the world.

Of course there is only one known definition of the phrase Wtf and that, of course is Wilbur, that frigg-nugget.

something you are likely to say after reading a few definitions in urban dictionary.

1. What the fuck.
2. World Tae Kwon Do Federation

an acronym for "what the fuck", commonly used when one hears something that does not make any sense whatsoever or when one hears something that is so weird/random/uncommon that they feel they must say something equally random.

Stands for What The Fuck.