May also be used in boredom.
Jill: Where is bob? and what is that smell coming from the basement?
guy: so... wanna hang out?
bored guy: asdfasdfasdf
2. Something that a weirdo would say when you step on their toes or slap them.
3. A secret code not yet decrypted.
"asdfasdfasdf! You stepped on my toes!"
The nerd sits quietly staring at the screen trying to find the hidden meaning of... "asdfasdfasdf"