on the sly

Also found in: Medical, Idioms.

sly

 (slī)
adj. sli·er (slī′ər), sli·est (slī′ĕst) also sly·er or sly·est
1. Clever or cunning, especially in the practice of deceit.
2. Stealthy or surreptitious: took a sly look at the letter on the table.
3. Playfully mischievous: a sly laugh.
Idiom:
on the sly
In a way intended to escape notice: took extra payments on the sly.
[Middle English sleigh, from Old Norse slœgr.]
sly′ly adv.
sly′ness n.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Adv.1.on the sly - in a furtive manner; "the soldiers were furtively crawling through the night"
furtively
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
Translations
References in classic literature
You believe in a palace of crystal that can never be destroyed--a palace at which one will not be able to put out one's tongue or make a long nose on the sly. And perhaps that is just why I am afraid of this edifice, that it is of crystal and can never be destroyed and that one cannot put one's tongue out at it even on the sly.
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