1. Cheerfully irresponsible
   - carefree, devil-may-care, freewheeling, happy-go-lucky, harum-scarum 
2. Dazed from or as if from repeated blows
   "slaphappy with exhaustion"
   - punch-drunk, silly

See also: confused, irresponsible

• brier
• brierpatch
• brierwood
• briery
• brig
• brigade
• brigadier
• brigadier general
• brigand
• brigandage
• brigandine
• brigantine
• Brigate Rosse
• Brigham Young
• bright
• bright as a new penny
• bright blue
• bright side
• bright spark
• Bright's disease
• bright-eyed
• bright-eyed and bushy-tailed
• bright-red
• brighten
• brightly