snoop

verb

1. To be devious and cunning so as not to be seen.
2. To secretly spy on or investigate, especially into the private personal life of others.

   “If I had not snooped on her, I wouldn't have found out that she lied about her degree.”

3. (UK, dated, slang)To steal.

   “'What on earth do Coker and his parcel of tuck matter to us? You're not thinking of snooping his tuck, I suppose, like Bunter.'”

noun

1. The act of snooping.
2. One who snoops.

   “Be careful what you say around Gene because he's the bosses' snoop.”

3. A private detective.

   “She hired a snoop to find out if her husband was having an affair.”

   “Garrison's snoops regularly stole Kirkwood's mail while he was in New Orleans—only a federal offense.”