decay UK /dɪˈkeɪ/US /diˈkeɪ/verb 10noun 7forms 4 verb10 •To rot, to go bad.The cat's body decayed rapidly. •To cause to rot or deteriorate.The extreme humidity decayed the wooden sculptures in the museum's collection in a matter of years. •To deteriorate, to get worse, to lose strength or health, to decline in quality.The pair loved to take pictures in the decaying hospital on forty-third street. •To undergo bit rot, that is, gradual degradation. •To undergo software rot, that is, to fail to be updated in a changing environment, so as to eventually become legacy or obsolete. •To change by undergoing fission, by emitting radiation, or by capturing or losing one or more electrons; to undergo radioactive decay.Uranium decays to radium through a long series of steps with a cumulative half-life of 4.4 billion years. — 2005 •To undergo optical decay, that is, to relax to a less excited state, usually by emitting a photon or phonon. •To undergo prolonged reduction in altitude (above the orbited body).Damaged on lift-off, Skylab was left in orbit until its orbit decayed. — 2009 •Loss of airspeed due to drag. •Of an array: to lose its type and dimensions and be reduced to a pointer, for example when passed to a function. noun7 •Rot; any processes or result of organic matter being gradually decomposed, especially by microbial action.He spent himself, the labour of his axe, And leave it there far from a useful fireplace To warm the frozen swamp as best it could With the slow smokeless burning of decay. — 1914 •Deterioration of condition; loss of status, quality, strength, or fortune.Although the best room of the inn, it had the melancholy aspect of grandeur in decay, and was much too vast for comfort. — 1841 •Radioactive decay; decomposition of an atom or its nucleus. •Particle decay; decomposition of a sub-atomic particle. •Continuous decrease of a quantity. •Array decay. •(no longer used) Overthrow, destruction, ruin, death. formsdecayed · decaying · decayeth · decays