All right, I'll embarrass myself and play one for everyone.
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A polite, self-deprecating word used by the performer themselves before or after singing, playing, drawing, etc. Literally 'to present my ugliness'. Never used to describe someone else - saying 你献丑了 about another person would be an insult, not a compliment.
culture
Part of the Chinese repertoire of formulaic modesty (谦辞), alongside 拙作 ('my crude work'), 寒舍 ('my humble dwelling'), and 拙见 ('my poor opinion'). Saying 献丑了 even when you performed brilliantly is the expected courtesy.
