6. derisive mockery or the object of such mockery: to make sport of someone. 7. someone or something that is controlled by external influences: the sport of fate. 10. informal a person who leads a merry existence, esp a gambler: he's a bit of a sport.
Rust is a fungal disease that occurs on turf grasses when their growth is slowed. This usually happens in late summer or early fall, during periods of dry weather or when the grass is low on nitrogen. Lawn rust can weaken the vigor of the grass and open it to other diseases and turf problems.
From: Pest Problem Solver. Disease fungi take their energy from the plants on which they live. They are responsible for a great deal of damage and are characterized by wilting, scabs, moldy coatings, rusts, blotches and rotted tissue.