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]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "lurk":
   be latent, couch, creep, escape notice, gumshoe, hibernate, hide,
   lay wait, lie beneath, lie dormant, lie hid, lie in wait, lie low,
   make no sign, nightwalk, prowl, pussyfoot, shadow, skulk, slide,
   slink, slip, smolder, snake, sneak, stalk, steal, tiptoe,
   underlie



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

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)