What is "box wine"

n. a type of wine that is sealed in a plastic bladder and packaged in a cardboard box

Box wine (cask wine or boxed wine) is wine packaged in a bag-in-box. Wine is contained in a plastic bladder typically with an air-tight valve emerging from a protective corrugated fiberboard box. It serves as an alternative to traditional wine bottling in glass with a cork or synthetic seal. It is sometimes called goon, and goon bag in Australia.