Source : Webster's Revised Unabridged Dictionary (1913)

Sneak \Sneak\, v. t.
   To hide, esp. in a mean or cowardly manner. [Obs.]
   ``[Slander] sneaks its head.'' --Wake.

Sneak \Sneak\, n.
   1. A mean, sneaking fellow.

            A set of simpletons and superstitious sneaks.
                                                  --Glanvill.

   2. (Cricket) A ball bowled so as to roll along the ground; --
      called also {grub}. [Cant] --R. A. Proctor.

Sneak \Sneak\ (sn[=e]k), v. i. [imp. & p. p. {Sneaked}
   (sn[=e]kt); p. pr. & vb. n. {Sneaking}.] [OE. sniken, AS.
   sn[=i]can to creep; akin to Dan. snige sig; cf. Icel.
   sn[=i]kja 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.

Source : WordNet®

sneak
     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}]
     [also: {snuck}]

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},
            {sneak(a)}, {sneaky}, {stealthy}, {surreptitious}]
     [also: {snuck}]

sneak
     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}]