The Collaborative International Dictionary of English v.0.48:

Lurk \Lurk\ (l[^u]rk), v. i. [imp. & p. p. Lurked (l[^u]rkt);
   p. pr. & vb. n. Lurking.] [OE. lurken, lorken, prob. a dim.
   from the source of E. lower to frown. See Lower, and cf.
   Lurch, a sudden roll, Lurch to lurk.]
   1. To lie hidden; to lie in wait.
      [1913 Webster]

            Like wild beasts, lurking in loathsome den.
                                                  --Spenser.
      [1913 Webster]

            Let us . . . lurk privily for the innocent. --Prov.
                                                  i. 11.
      [1913 Webster]

   2. To keep out of sight.
      [1913 Webster]

            The defendant lurks and wanders about in Berks.
                                                  --Blackstone.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lurk
    v 1: lie in wait, lie in ambush, behave in a sneaky and
         secretive manner [syn: lurk, skulk]
    2: be about; "The high school students like to loiter in the
       Central Square"; "Who is this man that is hanging around the
       department?" [syn: loiter, lounge, footle, lollygag,
       loaf, lallygag, hang around, mess about, tarry,
       linger, lurk, mill about, mill around]
    3: wait in hiding to attack [syn: ambush, scupper,
       bushwhack, waylay, lurk, ambuscade, lie in wait]

The Free On-line Dictionary of Computing (19 January 2023):

lurking
lurk
lurker

    The activity of one of the "silent
   majority" in a electronic forum such as Usenet; posting
   occasionally or not at all but reading the group's postings
   regularly.  This term is not pejorative and indeed is casually
   used reflexively: "Oh, I'm just lurking".  Often used in "the
   lurkers", the hypothetical audience for the group's
   flamage-emitting regulars.

   Lurking and reading the FAQ are recommended netiquette for
   beginners who need to learn the history and practises of the
   group before posting.

   (1997-06-14)