WordWeb Online

1. (of memory) deficient in retentiveness or range
   "a forgetful memory"
   - unretentive, short
    
2. Not mindful or attentive
   "while thus forgetful of his steps he stumbled"
   - unmindful, mindless
    
3. Failing to keep in mind
   "forgetful of her responsibilities"
   - oblivious

See also: amnesiac, amnesic, forgetfully, forgetfulness, heedfulness, inattentive, mindfulness

Encyclopedia: Forgetful