1. Lacking sense or discretion
   - rattlebrained, rattlepated, scatty [Brit] 
2. Guided by whim and fancy
   - flighty, flyaway, head-in-the-clouds

See also: foolish, frivolous

• francolin
• Francophil
• Francophile
• Francophobe
• francophone
• frangibility
• frangible
• frangibleness
• frangipane
• frangipani
• frangipanni
• franglais
• frank
• Highway Code
• highway engineer
• highway robbery
• highway system
• highwayman
• Higi
• hijab
• hijack
• hijacker
• hijacking
• Hijaz
• hijinks