sneak in WordNet English dictionary

1. make off with belongings of others
   pilfer  cabbage  purloin  pinch  abstract  snarf  swipe  hook  sneak  filch  nobble  lift 
   
2. to go stealthily or furtively
   "..stead of sneaking around spying on the neighbor's house"
   sneak  mouse  creep  pussyfoot 
   
3. pass on stealthily
   "He slipped me the key when nobody was looking"
   slip  sneak 
   
4. put, bring, or take in a secretive or furtive manner
   "sneak a look"; "sneak a cigarette"
   sneak 
   

1. someone acting as an informer or decoy for the police
   fink  snitch  snitcher  stoolpigeon  stool pigeon  stoolie  sneak  sneaker  canary 
   
2. someone who prowls or sneaks about; usually with unlawful intentions
   prowler  sneak  stalker 
   
3. a person who is regarded as underhanded and furtive and contemptible
   sneak 
   

1. marked by quiet and caution and secrecy; taking pains to avoid being observed
   "a furtive manner"; "a sneak attack"; "stealthy footsteps"; "a surreptitious glance at his watch"
   furtive  sneak  sneaky  stealthy  surreptitious