sneak

Someone who prowls or sneaks about; usually with unlawful intentions.

Someone acting as an informer or decoy for the police.

A person who is regarded as underhanded and furtive and contemptible.

Make off with belongings of others.

Pass on stealthily.

To go stealthily or furtively.

“..stead of sneaking around spying on the neighbor's house”

Put, bring, or take in a secretive or furtive manner.

“sneak a look”

“sneak a cigarette”

Marked by quiet and caution and secrecy; taking pains to avoid being observed.

“a sneak attack”