This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. superlative form of sly: most sly.

"Unfazed, newest recruit Josie Rourke begins her reign as artistic director with a wink of candlelight, the slyest pre-show mobile phone warning ever conceived, a gurgling sense of fun, and a Restoration comedy, which is a first for the Donmar."

slinking    black-tailed    man-form    gray-whiskered    wiliest