winter apple; apple sold during winter
Refers to apples that are harvested in late autumn and stored or sold during the winter months. Not a distinct variety, but a seasonal designation.
Winter apples taste especially good when eaten during the cold season.
Compound of 冬 (ふゆ, winter) and 林檎 (りんご, apple). The exact historical origin is uncertain, but it likely arose as a seasonal market term.