The starting 4 words at the 2nd alphabetical row of a keyboard, often typed when user is bored, hyperactive or having a stroke. The word is commonly typed in large amounts. By placing four fingers of your left hand on the 4 keys, you can repeat the word very quickly.
The word is also the title of the popular animation series "ASDF movie" by TomSka.
Dude I'm so bored asdfasdfasdfasdfasdfasdfasdfasdfasdfasdf.