流りゅう蛍けいMeanings1nounflying fireflyformal or literaryA formal or literary term for a firefly in flight, evoking a poetic image of light drifting through the air.夏なつの夜よる、流りゅう蛍けいが川かわ面もをかすめて飛とんでいた。On a summer night, flying fireflies skimmed over the river surface.