mò míng qí miào

莫名其妙

baffling; unable to make head or tail of something; without rhyme or reason; inexplicable

Example:

他为什么讲这番话, 真叫人莫名其妙。
Tā wèishénme jiǎng zhè fān huà, zhēn jiào rén mòmíngqímiào.
It is quite baffling that he should make such remarks.

她莫名其妙地哭了起来。
Tā mòmíngqímiào de kū le qǐlai.
Quite unaccountably she burst into tears

他说了几句莫名其妙的话
tā shuì le jī gōu mò míng qí miào de huà
He said some mysterious words.