1. (

• rattlebrained ,
• rattlepated ,
• scatterbrained ,
• scatty

) lacking sense or discretion; "his rattlebrained crackpot ideas"; "how rattlepated I am! I've forgotten what I came for"- Glenway Westcott ;

2. (

• flighty ,
• flyaway ,
• head-in-the-clouds ,
• scatterbrained

) guided by whim and fancy; "flighty young girls" ;