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]

Moby Thesaurus II by Grady Ward, 1.0:

81 Moby Thesaurus words for "lurking":
   abeyant, about to be, already in sight, approaching, at hand,
   between the lines, brewing, close, close at hand, coming, covert,
   cryptic, delitescent, doggo, dormant, esoteric, forthcoming,
   furtive, future, gathering, going to happen, hibernating, hidden,
   hidden out, immediate, imminent, impendent, impending, in ambush,
   in danger imminent, in hiding, in prospect, in reserve, in store,
   in the cards, in the offing, in the wind, in the wings, in view,
   instant, latent, looming, lowering, menacing, muffled, mystic,
   near, near at hand, nearing, obfuscated, obscured, occult,
   on the horizon, on tiptoe, overhanging, possible, potential,
   preparing, prowling, pussyfoot, pussyfooted, quiescent, skulking,
   sleeping, sneaking, stealing, stealthy, submerged, surreptitious,
   that will be, threatening, to come, under cover, under the surface,
   underlying, unmanifested, upcoming, veiled, virtual, waiting,
   waiting concealed



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)