adjective (eerier, eeriest)

strange and frightening:

得体の知れない, 奇妙な; 〈光･音楽･音･自然現象などが〉気味の悪い, 〈一致した状態･類似性などが〉不気味な; 陰鬱な.

e.g. an eerie green glow in the sky.

eeriness |ˈirēnəs| noun

Middle English (originally northern English and Scots in the sense ‘fearful’): probably from Old English earg ‘cowardly’, of Germanic origin; related to German arg.