noun
opening (a bottle, container); broaching
Refers to the act of opening something sealed, especially a bottle or container, for the first time.
ワインの口開けをお願いします。
Please open the wine bottle.
noun
beginning; opening; commencement; first sale
Used for the start of an event, sales period, or season. Often implies the very first instance or transaction.
Today is the start of the sale, and there's been a line since morning.
新商品の口開けの売れ行きは好調だ。
The initial sales of the new product are strong.
Compound of 口 (mouth, opening) and 開け (opening, from 開ける). The literal meaning 'opening the mouth' extended to opening containers and then to the beginning of events or sales.