adj. sli·er (slīər), sli·est (slīĕst) also sly·er or sly·estIdiom:
1. Clever or cunning, especially in the practice of deceit.
2. Stealthy or surreptitious: took a sly look at the letter on the table.
3. Playfully mischievous: a sly laugh.
on the sly
In a way intended to escape notice: took extra payments on the sly.
[Middle English sleigh, from Old Norse slœgr.]
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Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
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