featherbrained (adj.)

• brainless
• capricious
• dizzy
• empty-headed
• fickle
• flighty
• fluffy
• frivolous
• frothy
• gaga
• giddy
• harebrained
• impulsive
• light
• rattlebrained
• rattlepated
• scatterbrained
• shallow
• silly
• skittish
• superficial
• thoughtless
• volatile
• whimsical
• witless