1. Lacking sense or discretion
   "his rattlebrained crackpot ideas"
   - rattlepated, scatterbrained, scatty [Brit]

See also: foolish

• king protea
• king salmon
• king vulture
• king whiting
• King William pine
• King's Counsel
• King's English
• king's evil
• king's ransom
• king's spear
• king-size
• king-sized
• kingbird
• kingbolt
• kingcraft
• kingcup
• kingdom
• kingdom Animalia
• kingdom come
• kingdom Fungi
• kingdom Monera
• Kingdom of Belgium
• Kingdom of Bhutan
• Kingdom of Cambodia
• Kingdom of Denmark