Peter Saint-Andre suggested that the term "persona" might get the
point across better in general use, and I tend to agree. Certainly in
web-based communities the notion of an "avatar" is mostly just a name
and an icon.
Here are some definitions from WordNet:
"avatar"
# {10418302} <noun.person>[18] S: (n) embodiment#1 (embodiment
%1:18:00::), incarnation#1 (incarnation%1:18:00::), avatar#1 (avatar
%1:18:02::) (a new personification of a familiar idea) "the embodiment
of hope"; "the incarnation of evil"; "the very avatar of cunning"
# {09530238} <noun.person>[18] S: (n) avatar#2 (avatar%1:18:00::) (the
manifestation of a Hindu deity (especially Vishnu) in human or
superhuman or animal form) "the Buddha is considered an avatar of the
god Vishnu"
"persona"
# (1) {05929008} <noun.cognition>[09] S: (n) character#4 (character
%1:09:01::), role#2 (role%1:09:00::), theatrical role#1
(theatrical_role%1:09:00::), part#7 (part%1:09:01::), persona#1
(persona%1:09:00::) (an actor's portrayal of someone in a play) "she
played the part of Desdemona"
# {04677716} <noun.attribute>[07] S: (n) persona#2 (persona
%1:07:00::), image#2 (image%1:07:00::) ((Jungian psychology) a
personal facade that one presents to the world) "a public image is as
fragile as Humpty Dumpty"