(n) the event of leaving school, work, or the house to quickly pick up food for and/or with one's friends. It may occur in groups or it may be done solo, but if it is done alone, the food is brought back to the person's friends.
Person 1: Jimmy went on a food run during his lunch break.
Person 2: But his lunch break is only 20 minutes!
When you plan a long run, typically between 7 and 20 miles, to end at a destination for food you would only eat after having finished a long run.
"I mapped a 10-mile food run from lower Manhattan to Bensonhurst because I wanted to reward myself with a giant bowl of pho and vietnamese snacks at the end. (Nevermind that that I live less than a mile away from perfectly delicious pho!)"