1. Damaged by decay; hence unsound and useless
   "a decayed foundation";
   - rotten, rotted

1. Fall into decay or ruin
   "The unoccupied house started to decay";
   - crumble, dilapidate
    
2. Undergo decay or decomposition
   "The body started to decay and needed to be cremated"
    
3. (physics) lose a stored charge, magnetic flux, or current
   "the particles decayed during the nuclear fission process";
   - disintegrate, decompose

See also: unsound

Type of: change, change integrity

Encyclopedia: Decayed, missing, and filled teeth