WordNet (r) 3.0 (2006):

newbie
    n 1: any new participant in some activity [syn: newcomer,
         fledgling, fledgeling, starter, neophyte,
         freshman, newbie, entrant]

The Jargon File (version 4.4.7, 29 Dec 2003):

newbie
 /n[y]oo'bee/, n.

    [very common; orig. from British public-school and military slang variant
    of ?new boy?] A Usenet neophyte. This term surfaced in the newsgroup
    talk.bizarre but is now in wide use (the combination ?clueless newbie? is
    especially common). Criteria for being considered a newbie vary wildly; a
    person can be called a newbie in one newsgroup while remaining a respected
    regular in another. The label newbie is sometimes applied as a serious
    insult to a person who has been around Usenet for a long time but who
    carefully hides all evidence of having a clue. See B1FF; see also gnubie
    . Compare chainik, luser.


The Free On-line Dictionary of Computing (30 December 2018):

newbie
noob

    /n[y]oo'bee/ (Sometimes shorted to "noob") Originally
   from British public-school and military slang variant of "new
   boy", an inexperienced user.

   This term surfaced in the newsgroup news:talk.bizarre but
   is now in wide use.  Criteria for being considered a newbie
   vary wildly; a person can be called a newbie in one group
   while remaining a respected regular in another.  The label
   "newbie" is sometimes applied as a serious insult to a person
   who has been around for a long time but who carefully hides
   all evidence of having a clue.

   See BIFF.

   [Jargon File]

   (2007-08-02)