sneak

One who sneaks; one who moves stealthily to acquire an item or information.

"My little brother is such a sneak; yesterday I caught him trying to look through my diary."

A cheat; a con artist.

"I can't believe I gave that sneak $50 for a ticket when they were selling for $20 at the front gate."

Similar: con artist, trickster

An informer; a tell-tale.

To creep or go stealthily; to come or go while trying to avoid detection, as a person who does not wish to be seen.

"He decided to sneak into the kitchen for a second cookie while his mom was on the phone."

Similar: skulk

To take something stealthily without permission.

"I went to sneak a chocolate but my dad caught me."

(ditransitive) To stealthily bring someone something.

"She asked me to sneak her a phone next month."

In advance; before release to the general public.

"The company gave us a sneak look at their new electronic devices."

In a stealthy or surreptitious manner.

"I was able to get a sneak peek at the guest list."