Definition
A 'rusty rig' isn't a formal botanical term, but it could colloquially refer to old or neglected machinery used in agriculture or forestry, especially if it's reddish-brown from rust. Think of it as the beat-up tractor in a country song. It symbolizes age, hard work, and perhaps a bit of decay. It might represent an abandoned oil rig. It suggests something that was once functional is now deteriorated from disuse.