[1] : The Collaborative International Dictionary of English v.0.48

sneak \sneak\ sn=ek, v. i. imp.  p. p. sneaked
   sn=ekt; p. pr.  vb. n. sneaking. oe. sniken, as.
   snimaccan to creep; akin to dan. snige sig; cf. icel.
   snimackja to hanker after.
   1. to creep or steal away or about privately; to come or go
      meanly, as a person afraid or ashamed to be seen; as, to
      sneak away from company.
      1913 webster

            you skulked behind the fence, and sneaked away.
                                                  --dryden.
      1913 webster

   2. to act in a stealthy and cowardly manner; to behave with
      meanness and servility; to crouch.
      1913 webster
see also:
sneaked sneaking 

[2] : The Collaborative International Dictionary of English v.0.48

sneak \sneak\, v. t.
   to hide, esp. in a mean or cowardly manner. obs. "slander
   sneaks its head." --wake.
   1913 webster

[3] : The Collaborative International Dictionary of English v.0.48

sneak \sneak\, n.
   1. a mean, sneaking fellow.
      1913 webster

            a set of simpletons and superstitious sneaks.
                                                  --glanvill.
      1913 webster

   2. cricket a ball bowled so as to roll along the ground; --
      called also grub. cant --r. a. proctor.
      1913 webster
see also:
grub 

[4] : WordNet (r) 2.0

sneak
     adj : marked by quiet and caution and secrecy; taking pains to
           avoid being observed; "a furtive manner"; "a lurking
           prowler"; "a sneak attack"; "stealthy footsteps"; "a
           surreptitious glance at his watch"; "someone skulking
           in the shadows" syn: furtive, lurking, skulking,
            sneaka, sneaky, stealthy, surreptitious
     n 1: someone who prowls or sneaks about; usually with unlawful
          intentions syn: prowler, stalker
     2: someone acting as an informer or decoy for the police syn:
        fink, snitch, snitcher, stoolpigeon, stoolie, sneaker,
         canary
     v 1: to go stealthily or furtively; "..stead of sneaking around
          spying on the neighbor's house" syn: mouse, creep,
          steal, pussyfoot
     2: put, bring, or take in a secretive or furtive manner; "sneak
        a look"; "sneak a cigarette"
     3: make off with belongings of others syn: pilfer, cabbage,
         purloin, pinch, abstract, snarf, swipe, hook,
         filch, nobble, lift
     4: pass on stealthily; "he slipped me the key when nobody was
        looking" syn: slip
     also: snuck
see also:
furtive lurking skulking sneaka sneaky stealthy 
surreptitious prowler stalker fink snitch 
snitcher stoolpigeon stoolie sneaker canary 
mouse creep steal pussyfoot pilfer 
cabbage purloin pinch abstract snarf 
swipe hook filch nobble lift 
slip snuck 

[5] : Moby Thesaurus II by Grady Ward, 1.0

84 moby thesaurus words for "sneak":
   arrant coward, blackguard, caitiff, clandestine, couch, covert,
   cower, craven, crawl, creep, cringe, crouch, cur, dastard, devil,
   fink, furtive, glide, go on tiptoe, grass, grovel, gumshoe, heel,
   hole-and-corner, hush-hush, inch, inch along, informer, knave,
   lay wait, lie in wait, louse, lurk, nark, nightwalk, pad, poltroon,
   precious rascal, prowl, pussyfoot, quail, rapscallion, rascal,
   recreant, reptile, rogue, run, scalawag, scamp, scoundrel,
   scrabble, scramble, shadow, shirk, shithead, shyster, sidle, skulk,
   skunk, slide, slink, slip, slither, sly, smuggle, snake, sneaker,
   snitch, snook, spalpeen, stalk, steal, steal along, stealthy,
   stoolie, surreptitious, tippytoe, tiptoe, toad, undercover,
   villain, weasel, worm, worm along

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