The Collaborative International Dictionary of English v.0.48:

Skulk \Skulk\, v. i. [imp. & p. p. Skulked; p. pr. & vb. n.
   Skulking.] [Of Scand. origin; cf. Dan. skulke to spare or
   save one's self, to play the truant, Sw. skolka to be at
   leisure, to shirk, Icel. skolla. Cf. Scowl.]
   To hide, or get out of the way, in a sneaking manner; to lie
   close, or to move in a furtive way; to lurk. "Want skulks in
   holes and crevices." --W. C. Bryant.
   [1913 Webster]

         Discovered and defeated of your prey,
         You skulked behind the fence, and sneaked away.
                                                  --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

skulking
    n 1: evading duty or work by pretending to be incapacitated;
         "they developed a test to detect malingering" [syn:
         malingering, skulking]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "skulking":
   back-door, backstairs, clandestine, covert, cowering, cringing,
   doggo, feline, furtive, hidden out, hidlings, hole-and-corner,
   hugger-mugger, in ambush, in hiding, in the wings, lurking,
   on tiptoe, privy, prowling, pussyfoot, pussyfooted, quailing,
   quiet, shifty, slinking, slinky, sly, sneaking, sneaky, stealing,
   stealthy, surreptitious, under cover, under-the-counter,
   under-the-table, undercover, underground, underhand, underhanded,
   unobtrusive, waiting concealed