Refers to one's social standing, dignity, or reputation, especially in the context of not losing face. Common in phrases like メンツを保つ (to save face) or メンツが立たない (to lose face).
from Chinese miànzi
彼は部下の前でメンツを保とうとした。
He tried to save face in front of his subordinates.
そんなことをしたら、彼のメンツが丸つぶれだ。
If you do that, his reputation will be completely ruined.
In mahjong, a set of tiles declared as a combination (e.g., a pung or chow).
彼はすぐにメンツを鳴いて、手を進めた。
He quickly called a meld and advanced his hand.
The group of players participating in a mahjong game; often used when talking about gathering enough people to play.
今夜のメンツはいつもの三人と新人一人だ。
Tonight's lineup is the usual three plus one newcomer.
attendees; members; participants
Colloquial extension from mahjong; refers to the people present at a meeting, event, or gathering. Often used in casual conversation.
今日の飲み会のメンツはなかなか豪華だね。
Today's drinking party lineup is pretty impressive, isn't it?
I argued back in front of the boss and made him lose face.
We don't have enough players today, so we can't play mahjong.
He's always so worried about saving face that he can't apologize honestly.