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Synonyms

on the sly

Idioms  

  1. 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]

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The math-proficiency analysis suggests it may be doing so on the sly.

From The Wall Street Journal • Nov. 30, 2025

We were forbidden to speak Urdu, but my mother still taught us on the sly.

From New York Times • Mar. 1, 2024

You steal work from US writers on the sly, and you're blacklisted.

From Los Angeles Times • May 2, 2023

Sometimes, developers bought up units on the sly, knowing that control over assessments and expenditures could come as soon as a majority.

From Slate • Aug. 4, 2021

If we had one, I could befriend an actor or two, and get them to keep training me on the sly.

From "You Bring the Distant Near" by Mitali Perkins

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

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