on the sly

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Related to on the sly: get on, fall apart, catch up, stay put, turn up, called off


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.
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"
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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.