- The definition of sly is someone or something that is clever in a deceitful or cunning way.
An example of something that would be described as sly is a devious secret plot to win an award.
adjectiveslier or slyer, sliest or slyest
- Dialectal skillful or clever
- skillful at trickery or deceit; crafty; wily
- showing a secretive, crafty, or wily nature; cunningly underhanded
- mischievous in a playful way; roguish
Origin of slyMiddle English sley ; from Old Norse slœgr, clever, cunning, literally , able to strike ; from base of slā and amp; Old English slean, to strike: see slay
on the sly
adjectivesli·er , sli·est also sly·er or sly·est
- Clever or cunning, especially in the practice of deceit.
- Stealthy or surreptitious: took a sly look at the letter on the table.
- Playfully mischievous: a sly laugh.
Origin of slyMiddle English sleigh, from Old Norse slœgr.
(comparative slier or slyer, superlative sliest or slyest)
From Middle English sly, sley, from Old Norse slÇ£gr, slÅ“gr (â€œsly, cunningâ€, literally â€œcapable of hitting or strikingâ€), from Proto-Germanic *slÅgiz (â€œlively, agile, cunning, sly, strikingâ€), from Proto-Indo-European *slak- (â€œto hit, throwâ€). Cognate with Icelandic slÃ¦gur (â€œcrafty, slyâ€), Norwegian Nynorsk slÃ¸g (â€œslyâ€), German schlau (â€œclever, craftyâ€). Related to sleight, slay.