Definitions of decay:

• noun:   the organic phenomenon of rotting
• noun:   a gradual decrease; as of stored charge or current
• noun:   the process of gradually becoming inferior
• noun:   the spontaneous disintegration of a radioactive substance along with the emission of ionizing radiation
• noun:   an inferior state resulting from the process of decaying

  Example: "The corpse was in an advanced state of decay"

• verb:   undergo decay or decomposition

  Example: "The body started to decay and needed to be cremated"

• verb:   fall into decay or ruin

  Example: "The unoccupied house started to decay"

• verb:   lose a stored charge, magnetic flux, or current