[ slahy ]
/ slaɪ /
adjective, sly·er, sly·est.
cunning or wily: sly as a fox.
stealthy, insidious, or secret.
playfully artful, mischievous, or roguish: sly humor.
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on the sly, secretly; furtively: a tryst on the sly.
Origin of sly
1150–1200; Middle English sly, sley, from Old Norse slœgr “sly, cunning” (originally “able to strike, able to slay”); see slay
SYNONYMS FOR sly
sly·ly, adverbsly·ness, nounun·sly, adjective, un·sly·er, un·sly·est.un·sly·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for on the sly
/ (slaɪ) /
adjective slyer, slyest, slier or sliest
crafty; artfula sly dodge
insidious; furtivea sly manner
playfully mischievous; roguishsly humour
on the sly in a secretive manner
Derived Formsslyly or slily, adverbslyness, noun
Word Origin for sly
C12: from Old Norse slǣgr clever, literally: able to strike, from slā to slay
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
Idioms and Phrases with on the sly (1 of 2)
on the sly
Furtively, secretly, as in She's always eating cookies on the sly. The adjective sly, which means “cunning” or “crafty,” is here used as a noun. [c. 1800]
Idioms and Phrases with on the sly (2 of 2)
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.