[ slahy ]
See synonyms for sly on
adjective,comparative sly·er or sli·er [slahy-er], /ˈslaɪ ər/, superlative sly·est or sli·est [slahy-ist]. /ˈslaɪ ɪst/.
  1. cunning or wily: sly as a fox.

  2. stealthy, insidious, or secret.

  1. playfully artful, mischievous, or roguish: sly humor.

Idioms about sly

  1. on the sly, secretly; a tryst on the sly.

Origin of sly

First recorded in 1150–1200; Middle English sly, sley , from Old Norse slœgr “sly, cunning” (originally “able to strike, able to slay”); see slay

Other words for sly

Opposites for sly

Other words from sly

  • slyly, adverb
  • slyness, noun
  • un·sly, adjective, un·sly·er, un·sly·est.
  • un·sly·ly, adverb
  • un·sly·ness, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use sly in a sentence

  • Once there was a bad boy named Tom, and the older he grew, the wiser and slyer he thought himself.

    Bluebeard | Clifton Johnson
  • When exceptional circumstances compel me to take an opposite course, there isn't a slyer fox alive than I am.

    No Name | Wilkie Collins
  • And he looked hard at Hallvard, who was the slyer of those two.

  • As a rule, the quieter a man is the slyer he is, and the more he means mischief.

  • But of course he knew this, too; so I did not evade the slyer intent of his question.

    The Little Red Foot | Robert W. Chambers

British Dictionary definitions for sly


/ (slaɪ) /

adjectiveslyer, slyest, slier or sliest
  1. crafty; artful: a sly dodge

  2. insidious; furtive: a sly manner

  1. playfully mischievous; roguish: sly humour

  1. on the sly in a secretive manner

Origin of sly

C12: from Old Norse slǣgr clever, literally: able to strike, from slā to slay

Derived forms of sly

  • slyly or slily, adverb
  • slyness, noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Idioms and Phrases with sly


see on the sly.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.