na-adjective, noun
Rare, literary word for something eerie, uncanny, or inexplicably odd. Not used in everyday conversation; modern equivalents include 不思議な or 奇妙な.
その古い屋敷には面妖な噂が絶えない。
Weird rumors never cease about that old mansion.
彼の話はどうも面妖で、にわかには信じがたい。
His story is somehow mysterious and hard to believe right away.
The kanji 面妖 are ateji (phonetic) for the reading めんよう. The exact origin of the word is uncertain, but it is a rare literary term.