cunning
Meaning: sly, clever at being deceitful
Usage: The general devised a cunning plan to surprise the enemy.
wily
Meaning: crafty, sly
Usage: Though they were not the strongest of the Thundercats, wily Kit and Kat were definitely the most clever and full of tricks.
furtive
Meaning: secretive, sly
Usage: Maya cast a furtive glance at her notes before answering the question.
devious
Meaning: not straightforward, deceitful
Usage: Not wanting to be punished, the devious girl blamed the broken vase on the cat.
guile
Meaning: deceitful, cunning, sly behavior
Usage: Because of his great guile, the politician was able to survive scandal after scandal.