To do something on the sly is doing something sneakily, like a ninja.
"Check it out, I stole this on the sly."
"I'm skiving off school, on the sly of course."
by Naevai April 03, 2009
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Shorter, easier way of saying
'on the sly' meaning 'in secret' or 'not obviously'.

Usually pronounced like 'ont sly' by people from the north of england.
Chloe: aww look at you, you're well excited on sly!
Amy: I so am not!!
by cocacolaprincess21 August 07, 2007
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To do something cunningly, preferably without any one seeing, apart from your best mate to prove you did it
"Hey Jo, see that girl there? Well we danced and she is now carrying my child!!!"
" Slllly!"
by Jizz muffin May 20, 2003
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secretive, being very smooth or mischevious
Wow Kelly you are one sly dog

Did you see her jump that kid, she was so sly

by Estafuton February 28, 2009
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so like when I'm imagining "sly" I just see a real slick looking dude just posted up against a suspicious building under a shadow.. zoom in and the fucker has a tooth pick in his mouth just so effortlessly sweet
that nigga think he so sly but he's white so...
by young wells master September 12, 2013
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A slang term for a man who is more sexually attracted to other men than to women. It is not usually derogatory but it can be sometimes. It has the connotation of a gentleman who is educated and refined and who does not "broadcast" their orientation.
"I don't think Chris wants to have sex with you Lauren - he's sly."
"I was totally plastered and I wanted to have sex with this really really hot guy, but it turned out he's sly, so he just walked me back to my dorm instead."
"I can never make friends with guys unless they're sly. Otherwise they are always staring at my breasts."
by Mark Williamson November 06, 2006
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