http://dictionary.reference.com/wordoftheday/archive/2010/09/15.html 1. Cunning; crafty; sly.
2. Obsolete . A person who is preeminent; a chief.
noun:
1. A curved masonry construction for spanning an opening.
Quotes:
Shimell, an opera singer by trade, brings an arch theatricality to his role, making Miller sit comfortably as both a pompous author and a withdrawn husband.
-- Michael Leader, "'Certified Copy' Review," DenofGeek.com, September, 2010
Janney's performance is arch and knowing, as she mocks the mother who dispenses anti-depressants to her kids like candy and eventually tells them, "I lied to you because I love you."
-- Bret Harte, "'Life During Wartime' Review," Danville Express, August, 2010
Origin:
Arch originally meant "chief," as in an archangel , but took on the sense of "mischievous" in the 1660s.