to decompose and fall out. If you don't clean your teeth regularly, they'll rot out! Some of the rafters in the shed rotted out, but we replaced them easily.
1. To become completely hollow or ruined by decay or decomposition: If you don't see a dentist, your teeth will rot out. The abandoned building might collapse because its walls have rotted out.
2. To cause something to become completely hollow or ruined by decay or decomposition: The water from the leaky sink rotted out the floor boards. All that candy will rot your teeth out.