ga ‧ ga /ˈɡɑːɡɑː/ BrE AmE adjective [not before noun] informal
[ Date: 1900-2000 ; Language: French ; Origin: gaga 'stupid person' ]
1 . an insulting word used to describe someone who is confused because they are old:
Sid keeps forgetting my name. I think he’s going a bit gaga.
2 . having a strong but often temporary feeling of love for someone SYN infatuated
gaga about/over
I can’t imagine why Susan is so gaga about him.