Definition of "Sneak" :
noun: someone acting as an informer or decoy for the police
noun: someone who prowls or sneaks about; usually with unlawful intentions
noun: a person who is regarded as underhanded and furtive and contemptible
verb: to go stealthily or furtively
"..stead of sneaking around spying on the neighbor's house."
verb: pass on stealthily
verb: make off with belongings of others
verb: put, bring, or take in a secretive or furtive manner
"Sneak a look."
adjective: marked by quiet and caution and secrecy; taking pains to avoid being observed
"A sneak attack."