Antonyms of adj thoughtless

2 senses of thoughtless

Sense 1
thoughtless (vs. thoughtful) -- (showing lack of careful thought; "the debate turned into thoughtless bickering")

thoughtful (vs. thoughtless) -- (exhibiting or characterized by careful thought; "a thoughtful paper")
        => bemused, deep in thought (predicate), lost (predicate), preoccupied -- (deeply absorbed in thought; "as distant and bemused as a professor listening to the prattling of his freshman class"; "lost in thought"; "a preoccupied frown")
        => brooding, broody, contemplative, meditative, musing, pensive, pondering, reflective, ruminative -- (deeply or seriously thoughtful; "Byron lives on not only in his poetry, but also in his creation of the 'Byronic hero' - the persona of a brooding melancholy young man";)
        => cogitative -- (given to cogitation; "he looked at me with cogitative eyes")
        => well thought out (predicate) -- (resulting from careful thought; "the paper was well thought out")
        => deliberative -- (involved in or characterized by deliberation and discussion and examination; "a deliberative body")
        => excogitative -- (concerned with excogitating or having the power of excogitation)

Sense 2
thoughtless, uncaring, unthinking -- (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'")

INDIRECT (VIA inconsiderate) -> considerate -- (showing concern for the rights and feelings of others; "friends considerate enough to leave us alone")

Similarity of adj thoughtless

2 senses of thoughtless

Sense 1
thoughtless (vs. thoughtful) -- (showing lack of careful thought; "the debate turned into thoughtless bickering")
       => inconsiderate, unconsidered -- (without proper consideration or reflection; "slovenly inconsiderate reasoning"; "unconsidered words"; "prejudice is the holding of unconsidered opinions")
       => unreflective, unthinking, unthoughtful -- (not exhibiting or characterized by careful thought)
          Also See-> inconsiderate#1

Sense 2
thoughtless, uncaring, unthinking -- (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'")
       => inconsiderate (vs. considerate) -- (lacking regard for the rights or feelings of others; "shockingly inconsiderate behavior")