ambulatory snack vending in a theater or stadium
Refers to vendors walking through the aisles selling snacks and drinks during intermissions or breaks at theaters, stadiums, or similar venues.
I bought ice cream from an ambulatory vendor at the movie theater.
野球場の中売りはビールがよく売れる。
Beer sells well among the ambulatory vendors at the baseball stadium.
Compound of 中 (なか, 'inside') and 売り (うり, 'selling'), referring to selling inside a venue, specifically walking through the audience.