expression, noun
imminent danger; impending hardship
A classical Chinese-derived idiom (故事成語) meaning a crisis so urgent that there is no time to lose, like a fish in a drying rut. Rare in modern Japanese; mainly encountered in literary or historical contexts.
「轍鮒の急」とは、轍の水たまりで苦しむ鮒のように、差し迫った危難をいう故事成語だ。
"Tetsupu no kyū" is a classical idiom referring to imminent danger, like a crucian carp struggling in a puddle in a wagon rut.