the world > health and disease > ill health > animal disease or disorder > [adjective] > of animals;ill (3)
Of an animal, esp. a fish: diseased. Cf. measle, adj.
Of a plant or animal: in poor condition; not thriving, unhealthy; (also) not tending to thrive, weak, sickly. Now rare (in later use chiefly Englis…
colloquial. Cf. weed, n.1 9. With reference to the build of an animal (esp. a horse or dog): lean, leggy, and lacking in physical strength or stamina.