adv. 1. Lacking thought; careless; inconsiderate; rash; as, a thoughtless person, or act. [ 1913 Webster ]
2. Giddy; gay; dissipated. [ R. ] Johnson. [ 1913 Webster ]
3. Deficient in reasoning power; stupid; dull. [ 1913 Webster ]
Thoughtless as monarch oaks that shade the plain. Dryden. [ 1913 Webster ]
-- Thought"less*ly, adv. -- Thought"less*ness, n. [ 1913 Webster ]