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."