sneaker n.

An individual hired to break into places in order to test their security; analogous to tiger team. Compare samurai.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

Sneak"er (?), n.

1.

One who sneaks. Lamb.

2.

A vessel of drink. [Prov. Eng.]

A sneaker of five gallons.
Spectator.

© Webster 1913

Sneak"er (?), n.

1. [pl.]

Shoes with rubber or other soft soles which give no warning of one's approaching, esp. such shoes as are worn in games, as tennis. [Slang, U. S.]

2.

A punch bowl. [Obs.] Spectator.

© Webster 1913