scatterbrained

Adjective

• guided by whim and fancy
  • flighty young girls
    

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

Related words

• Synonyms: 
  flighty , flyaway , head-in-the-clouds , rattlebrained , rattlepated , scatty