THOUGHTLESS
thoughtless, uncaring, unthinking
(adjective) without care or thought for others; “the thoughtless saying of a great princess on being informed that the people had no bread; ‘Let them eat cake’”
thoughtless
(adjective) showing lack of careful thought; “the debate turned into thoughtless bickering”
Source: WordNet® 3.1
Etymology
Adjective
thoughtless (comparative more thoughtless, superlative most thoughtless)
Marked by or showing lack of due thought or care; careless.
Inconsiderate, inattentive.
Lacking thought or consideration.
Coordinate terms
• short-sighted
Source: Wiktionary
Thought"less, adv.
1. Lacking thought; careless; inconsiderate; rash; as, a thoughtless
person, or act.
2. Giddy; gay; dissipated. [R.] Johnson.
3. Deficient in reasoning power; stupid; dull.
Thoughtless as monarch oaks that shade the plain. Dryden.
– Thought"less*ly, adv.
– Thought"less*ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition