Sly/slaɪ/ Definition 1 of 4Pro Tip 1/3Negative Connotation Used to describe someone's dishonest behavior, indicating disapproval. Her sly tactics to avoid work were frowned upon. Pro Tip 2/3Discreet Action Indicates someone is acting with secrecy to achieve an often sneaky goal. He passed the note with a sly wink. Pro Tip 3/3Hidden Motives Implies that the person has an ulterior motive not immediately obvious. The salesman’s sly approach raised suspicions.