The Collaborative International Dictionary of English v.0.48:

Skulk \Skulk\, n. [Cf. Icel. skollr, skolli, a fox, and E.
   skulk, v.i.]
   A number of foxes together. --Wright.
   [1913 Webster] Skulk

The Collaborative International Dictionary of English v.0.48:

Skulk \Skulk\, Skulker \Skulk"er\, n.
   One who, or that which, skulks.
   [1913 Webster]

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):

skulk
    v 1: lie in wait, lie in ambush, behave in a sneaky and
         secretive manner [syn: lurk, skulk]
    2: avoid responsibilities and duties, e.g., by pretending to be
       ill [syn: malinger, skulk]
    3: move stealthily; "The lonely man skulks down the main street
       all day"

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "skulk":
   army, bunch, clock watcher, colony, couch, cower, creep, cringe,
   crouch, dodge, dog it, drift, drive, drove, duck, duck duty,
   eye-servant, flock, gam, gang, get out of, goldbrick, goldbricker,
   goof off, gumshoe, herd, host, kennel, lay wait, lie in wait,
   litter, lurk, malinger, malingerer, nightwalk, not pull fair,
   old soldier, pack, pod, pride, prowl, pussyfoot, quail, school,
   shadow, shirk, shirker, shoal, skulker, slack, slacker,
   slide out of, slink, slip, slip out of, sloth, snake, sneak,
   sneak out of, soldier, stalk, steal, tax dodger, tiptoe, trip,
   troop, truant, welsh, welsher