on the sly

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

“They want me to go in with them on the sly,” says Colonel Sellers, the anti-hero of that novel.

From Salon

In contravention of their oath, the men make advances on the sly and the wary women prank them to test their mettle.

From New York Times

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

From New York Times

He was paroled from detention but banned from work and national health insurance, though he worked on the sly until about eight years ago, when the government started to tighten controls over parolees.

From Los Angeles Times

During the height of Prohibition, people knew they could get booze on the sly: in speakeasies, say, or as “medicine” prescribed by pharmacists.

From Los Angeles Times

Related Words

• clandestinely www.thesaurus.com
• covertly 
• furtively 
• personally 
• privately www.thesaurus.com
• quietly 
• stealthily 
• surreptitiously