medium beer mug
Refers to a medium-sized beer mug, typically around 400–500 ml, often used in Japanese pubs (izakaya).
See also: ジョッキ
とりあえず中ジョッキでお願いします。
I'll start with a medium beer mug, please.
Formed from 中, “medium,” and ジョッキ, “beer mug.” ジョッキ was borrowed from Dutch jok, “drinking cup.”