On The Sly Edit Meaning

1.

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."

See sneaky, stealth, sly, skive

2.

To be on the sly, the active of sly. You can do something on the sly, maybe stealing something funny and legendary, like mine and Jimbo's road bollard. You could also have 'slying it'

"We took that bollard on the sly"

"Tonight we're slying it/on the sly"

"Come on lads, here we go, on the sly on the sly"

See on the sly, sly, fox, dog, sly dog