Sly is an adjective, meaning one of the following:

1. Clever in practical matters.
2. Hiding ones true intentions or goals.

Its synonyms are "cunning" and "roguish".Sly is also a proper masculine name, short for Sylvester. It is the name of several famous persons:

• Sly Stone, American musician, frontman for Sly & the Family Stone
• Sylvester "Sly" Stallone, American actor.
• Sylvain Grenier, Canadian professional wrestler.
• William Sly, Elizabethan actor and colleague of William Shakespeare.

Sly is the title of an opera by Ermanno Wolf-Ferrari.Sly is also the first name of the main protagonist in the games:

• Sly Cooper and the Thievius Raccoonus
• Band of Thieves
• Honor Among Thieves