noun
drinking at home; home drinking
Casual term for drinking alcohol at home or in a private room, often with friends, as opposed to going out to bars.
今夜は外に出ずに部屋飲みしよう。
Let's drink at home tonight instead of going out.
部屋飲みだと安く済むから好きだ。
I like drinking at home because it's cheaper.
Synonym also meaning drinking at home; 部屋飲み can emphasize drinking in one's room specifically, while 宅飲み is broader.
Compound of 部屋 (room) and 飲み (drinking), from 飲む (to drink). A modern casual coinage.