near the knuckle
US /nɪr ðə ˈnʌkəl/
UK /nɪr ðə ˈnʌkəl/

1.
過火, 不雅, 粗俗
almost offensive or rude, especially because of being sexual or involving rude humor
:
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His jokes were a bit near the knuckle for the family gathering.
他的笑話對家庭聚會來說有點過火了。
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The comedian's routine was quite near the knuckle, but the audience loved it.
這位喜劇演員的表演相當過火,但觀眾很喜歡。