不明

not clear / unknown / to fail to understand

no; not so / (bound form) not; un-

Ming Dynasty (1368-1644) / surname Ming / Ming (c. 2000 BC), fourth of the legendary Flame Emperors, 炎帝[Yan2 di4] descended from Shennong 神農|神农[Shen2 nong2] Farmer God

bright / opposite: dark 暗[an4] / (of meaning) clear / to understand / next / public or open / wise / generic term for a sacrifice to the gods

unaccounted / unknown whereabouts

of unknown origin

obscure / dubious / shady

unidentified origin / no-one knows where it comes from / of dubious background

although I don't understand it, it seems pretty awesome (Internet slang)

unidentified flying object (UFO)

missing / lost

not understanding things (idiom); devoid of sense

not to understand the situation / unaware of the ins and outs

indefinite / unclear