The coyote, or prairie-wolf, is the slyest animal that walks on four legs.
It's the slyest trick the old fox has ever tried to play on us.
He is perhaps the slyest of animals—more sly than a fox, more obstinate than an English mule, and as timid as a squirrel.
So they learned lots—and the slyest scoundrels learned the most.
She would wheedle things out of her mistress in the slyest way.
When buckled down to his work he became the slyest and cleverest of diplomats.
But the slyest and wisest of animals and men are liable at times to overreach themselves.
But my Uncle Diego is the slyest Galician born in this century.
He makes merry over the weaknesses of those who follow the craft of Old Izaak, always with the slyest of genial manners.
To tell the truth, human beings are the slyest and crudest of animals.
c.1200, "skillful, clever, dexterous," from Old Norse sloegr "cunning, crafty, sly," from Proto-Germanic *slogis (cf. Low German slu "cunning, sly," German schlau), probably from base *slak- "to strike, hit" (see slay (v.)), with an original notion of "able to hit." Cf. German verschlagen "cunning, crafty, sly," schlagfertig "quick-witted," literally "strike-ready," from schlagen "to strike." A non-pejorative use of the word lingered in northern English dialect until 20c. On the sly "in secret" is recorded from 1812. Sly-boots "a seeming Silly, but subtil Fellow" is in the 1700 "Dictionary of the Canting Crew."