1. 糊涂的；迷糊的；（尤指）老朽的
If you say that someone is gaga, you mean that they cannot think clearly any more, especially because they are old.

2. 着迷的；狂热的
If someone goes gaga over a person or thing, they like them very much.

1. intensely enthusiastic about or preoccupied with

e.g. crazy about cars and racing
he is potty about her

Synonym: crazywilddotty

2. mentally or physically infirm with age

e.g. his mother was doddering and frail

Synonym: dodderingdodderysenile