Gaga/ˈɡɑːɡɑː/ Definition 1 of 3Pro Tip 1/3Youthful Slang Often used among young people to express excitement about trends or celebrities. Teens went gaga over the latest video game release. Pro Tip 2/3Colloquial Expression Not used in formal writing or speech; more common in casual conversation. I'm going gaga for this new bubble tea spot downtown. Pro Tip 3/3Pop Culture Reference Can be used to describe a fad or craze that's popular for a brief time. Everyone is gaga over the dance challenge on social media.