inane, unreasonable, brainless, blank, unoccupied, mindless, thoughtless, unthinking, empty-headed, fatuous, vacuous, illogical, vacant.

lumpen, courtesy, thoughtless, careful, uncaring, inconsiderate, unreflective, lumpish, disregardful, unthinking.

The admiral, however, was not a man to be much influenced by the sayings of the unthoughtful and the unlearned. - "The Life of Columbus", Arthur Helps.

No, said the young man, though I appear unthoughtful in your eyes, O, servile race of flatterers! - "Eastern Tales by Many Story Tellers", Various.

What makes Wilson so irritating to the unthoughtful is that he operates exclusively upon reason, not upon passion. - "The Haunted Bookshop", Christopher Morley.

unthoughtfully, unthoughtfulness, unthought, unthought-of, untruthful, untoughened.