Someone who's an asshole on the internet. This same person probably can't get away with being an asshole in real-life. Most internet assholes are either too lazy or too retarded to hold a real job.
Man, that Timmy kid is such an internet asshole!
The Internet Asshole or "Homo Internetus" embodies a wealth of factoids backed up with little to no life experience, a crippling sense of agoraphobia, and a mild mix of tourettes and aspergers.
These are all drawn together with a slight judgmental grimace as if playing the part of the worlds observer. Pasty skin and a nasally tone are good compliments but not entirely necessary.
Nathaniel is such an internet asshole. A total Homo Internetus.