When a staunch vegetarian or vegan person accidentally eats meat, either because they thought the food was made of a meat substitute or because one of their friends tricked them.
Brooke: "Annette almost choked when I told her that those drummies she was wolfing down were made of REAL CHICKEN, not some bogus soy substitute. So she had an 'accidental meating.'"
Greg: "Wow. I've never seen her eat actual meat before. Guess we can't let her live that one down!"