Buying food and eating it (often between meals), especially children buying snacks on the way home from school; can be used as 'buy-and-eat' or 'to snack by buying food'.
放課後に友達とコンビニで買い食いをしてから帰った。
After school I went home after buying snacks with friends at the convenience store.
お腹が空いていたので、市場で串焼きを買い食いした。
I was hungry, so I bought and ate a skewer at the market.
親は子供の買い食いを心配して、夕飯前にはお金を持たせないことがある。
Parents sometimes don't give their children money before dinner because they're worried they'll buy snacks.