The term "sneak thief" has been in use for a long time and is still commonly used to describe someone who steals something discreetly. However, there are several other words we can use to describe a sneak thief. Some of the synonyms include pilferer, burglar, pickpocket, thief, and robber. A pilferer is someone who steals things worth little value, while a burglar is someone who sneaks into a building to steal something valuable. A pickpocket is a thief who steals from someone's pockets and a robber is someone who steals by force. By using these synonyms, we can add variety and richness to our vocabulary while describing someone who steals secretly.