D defs.my
Entry 2 senses Webster, 1913

gaga

· IPA /ˈɡɑːɡɑː/
01 adj. mentally or physically infirm with age.
  1. 1.
    mentally or physically infirm with age.
  2. 2.
    marked by foolish or unreasoning fondness; as, gaga over his girlfriend.