HSK 7-9
莫名其妙
mòmíngqímiào(idiom) baffling; bizarre; without rhyme or reason; inexplicable
他莫名其妙地取消了约会。
Tā mòmíngqímiào de qǔxiāo le yuēhuì.
He inexplicably canceled the appointment.
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Appears across levels (7-9) in the HSK 3.0 word list.