[in Hindu mythology, the incarnation of a god]
1. Among people working on virtual reality and cyberspace interfaces, an avatar is an icon or representation of a user in a shared virtual reality. The term is sometimes used on MUDs.
2. [CMU, Tektronix] root, superuser. There are quite a few Unix machines on which the name of the superuser account is ‘avatar’ rather than ‘root’. This quirk was originated by a CMU hacker who found the terms root and superuser unimaginative, and thought ‘avatar’ might better impress people with the responsibility they were accepting.