いきぐされ
(fish) appearing fresh but actually gone bad
Noun
早はやく帰かえった方ほうがいい、暑あついから。サバは、生いき腐ぐされとも言いわれるくらい足あしが早はやい。
It's hot, so you'd better head back quickly. Mackerel goes off so fast that they coined 'fresh-looking rotten fish'.