What does sly mean?
Sly describes a person, action, or expression that is crafty, furtive, or playfully mischievous. In its more negative sense, it suggests someone who uses deception or indirect methods to gain an advantage: a sly bargain, a sly trick, or a sly competitor. In more lighthearted contexts, especially with a look, smile, glance, or remark, it can indicate playful humor or knowing mischief rather than serious dishonesty. The word is useful because it captures a subtle form of indirectness: behavior that may appear innocent while suggesting calculation or secret amusement. It is understood throughout Britain and the United States and can be used in formal writing as well as conversation, though its strongest everyday associations are often informal and character-based.
adjectiveSly means crafty and deceptive, using trickiness or concealment to gain an advantage. It can also describe someone or something furtive, or a playful and mischievous look, smile, or remark.
- Crafty and deceptive, using trickiness or concealment to gain an advantage.
- Furtive or secretive, especially in movement or behavior.
- Playfully mischievous, especially in a look, smile, or remark.
"She gave him a sly smile that suggested she knew more than she was saying."
"The sly fox found a way into the henhouse without being noticed."
"He gave her a sly grin before changing the subject."
The word looks modern, but its core meaning—crafty or cunning—comes from the Old English word sleg.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does sly come from?
The word comes from Old English sleg, an adjective meaning crafty or cunning, and appeared in Middle English as sli before the modern spelling became established. It is generally traced to a Germanic root associated with craftiness. Related forms include sleight and sleuth, although their meanings developed in different directions.
Related word forms
How sly is actually used
Sly is common in both formal and informal English. Its connotation ranges from dishonest scheming to harmless playful cunning, depending on context.
Easily confused with sly
Sly is an adjective describing a quality, while slily is an adverb describing how an action is performed.