taru-adjective, adverb taking the 'to' particle
trailing (clouds); thick; heavy
Literary, classical adjective describing clouds or mist that hang low and thick, often with a sense of trailing or spreading heavily. Used in the form 靉靆たる or 靉靆として.
山の頂に靉靆たる雲がかかっていた。
Thick, trailing clouds hung over the mountain peak.
taru-adjective, adverb taking the 'to' particle
Literary, classical use for a gloomy, overcast emotional state. Also used in the 靉靆たる/として pattern.
彼の心は靉靆として晴れなかった。
His heart remained dark and gloomy, never clearing.
noun
Archaic noun for eyeglasses, derived from the cloudiness of early lenses. Not used in modern Japanese; the standard word is 眼鏡 (めがね).
江戸時代には「靉靆」という言葉で眼鏡を指した。
In the Edo period, the word 靉靆 referred to eyeglasses.
The modern standard word for eyeglasses; 靉靆 is an archaic synonym no longer in use.
The kanji 靉靆 are rare and used phonetically for the reading あいたい. The word originally described trailing clouds or mist, and by extension a gloomy mood. The archaic sense 'eyeglasses' likely arose from the cloudy appearance of early lenses. The exact derivation is uncertain.