best defined as if you have a boyfriend or girlfriend and are in a relationship. it's when all you do is hangout with each other and rarely come out and hangout with your own friends and are whipped and on that damn leash. it WILL swallow you whole. and it WILL get ya.
Will-"Have you seen Keith or Ang lately?"
Phil-"Nah man. They're in the unda. We probably won't be seeing them for a while."