glow up

To upgrade to a better version, specifically in terms of appearance, it refers to a person who has suddenly become more attractive. This phrase usually has pix next it: one of a person when they were younger, and one of how they look when they’re older. For example, “Wow, she really glowed up after high school.”
See also : online jargon  caking  millingo  BLAST  PLUR  
NetLingo Classification: Online Jargon