winsome \WIN-suhm\ (adjective) - 1 : Cheerful; merry; gay; light-hearted. 2 : Causing joy or pleasure; agreeable; pleasant.
"Colton had trouble curtailing a grin as he witnessed this innocuous confrontation, but when he found himself the recipient of an icy glance from the winsome brunette, he grew a bit perplexed until it suddenly dawned on him what she might be thinking now that the blonde had joined them." -- Kathleen E. Woodiwiss, 'The Reluctant Suitor'
Winsome is from Old English wynsum, from wynn, "joy" + -sum (equivalent to Modern English -some), "characterized by."