1. mentally or physically infirm with age

Similar word(s): old, doddering, doddery, senile

2. intensely enthusiastic about or preoccupied with

- gaga over the rock group's new album

Similar word(s): enthusiastic, crazy, dotty, wild

Sentences with gaga as an adjective:

- The elderly patients in the hospital were going gaga.

- You might go gaga if you stare at this screen too long.

- The girls were going gaga over the handsome new boy who joined the class.