screen name

a name or pseudonym (in the greater sense, a screen name is a cyber-pseudonym) generally used by users of net applications to identify themselves through proxy

screen name n.

A handle sense 1. This term has been common among users of IRC, MUDs, and commercial on-line services since the mid-1990s. Hackers recognize the term but don't generally use it.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.