sly

adjective

ˈslī 

slyer also slier ˈslī(-ə)r  ; slyest also sliest ˈslī-əst 

1

chiefly dialectal

a

: wise in practical affairs

b

: displaying cleverness : ingenious

2

a

: clever in concealing one's aims or ends : furtive

b

: lacking in straightforwardness and candor : dissembling

3

: lightly mischievous : roguish

a sly jest

slyly adverb

or less commonly slily

She slyly evaded the question.

slyness noun

see also:

on the sly

Synonyms of sly

• cunning
• cute
• subtle
• slick

Choose the Right Synonym for sly

sly, cunning, crafty, wily, tricky, foxy, artful, slick mean attaining or seeking to attain one's ends by guileful or devious means.

sly implies furtiveness, lack of candor, and skill in concealing one's aims and methods.

a sly corporate raider

cunning suggests the inventive use of sometimes limited intelligence in overreaching or circumventing.

the cunning fox avoided the trap

crafty implies cleverness and subtlety of method.

a crafty lefthander

wily implies skill and deception in maneuvering.

the wily fugitive escaped the posse

tricky is more likely to suggest shiftiness and unreliability than skill in deception and maneuvering.

a tricky political operative

foxy implies a shrewd and wary craftiness usually involving devious dealing.

a foxy publicity man planting stories

artful implies indirectness in dealing and often connotes sophistication or cleverness.

elicited the information by artful questioning

slick emphasizes smoothness and guile.

slick operators selling time-sharing

Examples of sly in a Sentence

the movie pairs a sly, dissembling ex-con with an upstanding, straight-arrow cop

why, you sly fellow! I had no idea you were planning my birthday party

Recent Examples on the Web

But it was filled with quicksilver, roller-coaster displays of virtuosity and the sly humor Lutoslawski and fellow Polish composer and pianist Andrzej Panufnik brought to their Paganini variations in its original 1941 iteration. — George Varga, San Diego Union-Tribune, 23 Aug. 2026

The Professional is a sly inversion of — and indulgent celebration of — action cliches, made at a time when action movies were ubiquitous but often redundant, featuring a succession of distinctly European stars like Schwarzenegger and Van Damme. — Declan Gallagher, Entertainment Weekly, 14 Aug. 2026

This argument made by the unknown soldier—which included a sly criticism of the USSR—affected how the war-crazy Zinn was starting to reassess the entire operation. — Literary Hub, 12 Aug. 2026

The men exude contentious authority in various ways, from the grandee’s circumspect command and Uncle Jeb’s sly omniscience to the mechanic’s viperish resentment and Billy’s acerbic flirtation. — Richard Brody, New Yorker, 11 Aug. 2026

Word History

Etymology

Middle English sleighe, sli, from Old Norse slœgr; akin to Old English slēan to strike — more at slay

First Known Use

13th century, in the meaning defined at sense 1a

Phrases Containing sly

• on the sly

Rhymes for sly

• ai
• aye
• bae
• bi
• buy
• by
• bye
• chai
• chi
• cry
• die
• dry

Kids Definition

sly

adjective

ˈslī 

slier or slyer ˈslī(-ə)r  ; sliest or slyest ˈslī-əst 

1

a

: clever at hiding one's goals or purpose

b

: tending to secrecy or concealment

2

: lightly mischievous

a sly smile

slyly adverb

slyness noun