what does sly mean? it's an adjective that means: 1- using tricks and dishonest methods to get what you want: he is sly and greedy. 2- showing that you know something that others do not know: a sly smile on the sly means secretly doing something you are not supposed to be doing: he's been smoking on the sly.

Two meanings...1.acting or done in a secret or dishonest way,often intending to trick people 2.suggesting that you know something secret that other people do not know

Dictionary def of sly: 1. Clever or cunning, especially in the practice of deceit. He is a sly thief. 2. Stealthy or surreptitious: He took a sly look at the letter on the table. 3. Playfully mischievous: She had a sly laugh. Idiom: on the sly In a way intended to escape notice: The policeman took extra payments on the sly.

Just use a dictionary.