WordWeb Online

1. Not mindful or attentive
   "while thus mindless of his steps he stumbled";
   - unmindful, forgetful
    
2. Lacking the thinking capacity characteristic of a conscious being
   "the shrieking of the mindless wind"
    
3. Requiring little mental effort
   "mindless tasks"
    
4. Devoid of intelligence or thought
   - vacuous, vacant
    
5. Not marked by the use of reason
   "mindless violence";
   - reasonless, senseless

See also: amnesiac, amnesic, daft [Brit, informal], dumb, foolish, heedfulness, imbecile, imbecilic, meaningless, mindfulness, nonintellectual, nonmeaningful, stupid, unintellectual, unreasonable

Antonym: aware

Encyclopedia: Mindless