Dictionary

To deteriorate, to get worse, to lose strength or health, to decline in quality.

Example: The pair loved to take pictures in the decaying hospital on forty-third street.

(of organic material) To rot, to go bad.

Example: The cat's body decayed rapidly.

(of an unstable atom) To change by undergoing fission, by emitting radiation, or by capturing or losing one or more electrons.

(of a quantum system) To undergo optical decay, that is, to relax to a less excited state, usually by emitting a photon or phonon.

Having undergone decay, rotted.

Example: The decayed remains of the pilot's shirt showed where the plane had been shot down.

Reduced in circumstances; having lost one's status or fortune.