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.

Music

• Sly (song), A single released by the Australian band, The Cat Empire.
• Sly is the title of an opera by Ermanno Wolf-Ferrari.
• Sly, a song by trip-hop group, Massive Attack
• Sly, a song by Herbie Hancock.

Sly is also the first name of the main protagonist in the games:

• Sly Cooper and the Thievius Raccoonus
• Sly 2: Band of Thieves
• Sly 3: Honor Among Thieves