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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

Some people were there to raise money on the sly, and given the big money behind WelcomeFest, it wasn’t a bad idea.

From Slate • Jun. 9, 2025

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

From Los Angeles Times • May 2, 2023

But with overfishing in the more populated areas - and the chance to earn big money selling fish on the sly - some fishermen encroach on indigenous land to find valuable species to sell.

From BBC • Jun. 13, 2022

So my plan was to sneak into the Keys on the sly and see what I might do behind the scenes.

From "Flush" by Carl Hiaasen

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.