sly

[ 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.

Idioms

    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

Related forms

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for on the sly

sly

/ (slaɪ) /

adjective slyer, slyest, slier or sliest

crafty; artfula sly dodge
insidious; furtivea sly manner
playfully mischievous; roguishsly humour

noun

on the sly in a secretive manner

Derived Forms

slyly 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)

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.