Un*think"ing, a.
1.
Not thinking; not heedful; thoughtless; inconsiderate; as, unthinking youth.
2.
Not indicating thought or reflection; thoughtless.
With earnest eyes, and round unthinking face,
He first the snuffbox opened, then the case.
Pope.
-- Un*think"ing*ly, adv. -- Un*think"ing*ness, n.
© Webster 1913.