noun cause of decay.
2. decay ·noun destruction; death.
3. decay ·vt to destroy.
4. decay ·vt to cause to decay; to impair.
5. decay ·noun gradual failure of health, strength, soundness, prosperity, or of any species of excellence or perfection; tendency toward dissolution or extinction; corruption; rottenness; decline; deterioration; as, the decay of the body; the decay of virtue; the decay of the roman empire; a castle in decay.
6. decay ·vi to pass gradually from a sound, prosperous, or perfect state, to one of imperfection, adversity, or dissolution; to waste away; to decline; to fail; to become weak, corrupt, or disintegrated; to rot; to perish; as, a tree decays; fortunes decay; hopes decay.