Someone who pretends to be a female in an online game such as Runescape, or just online in general, in order to gain attention/monetary gains in the game they're playing. Usually will do anything to keep the lie going, including having an e-bf and dumping them as soon as they start to suspect things.
Person A: Hey man, how's your e-gf?
Person B: Ah dude turns out she/he was a stilly1 all along :(
Person A: Sucks to be you bro.
See also andy1991