Megrim is a slender, lean European flatfish — chiefly Lepidorhombus whiffiagonis, the megrim or whiff — a left-eyed bottom-dweller of the North-East Atlantic whose thin, delicate, pure-white flesh is mild and gently sweet. Long undervalued in Britain, where most of the catch was exported, it is the prized fish known in Spain as gallo, much loved fried whole and crisp.