The Collaborative International Dictionary of English v.0.48:

Decay \De*cay"\, v. t.
   1. To cause to decay; to impair. [R.]
      [1913 Webster]

            Infirmity, that decays the wise.      --Shak.
      [1913 Webster]

   2. To destroy. [Obs.] --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Decay \De*cay"\, n.
   1. 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.
      [1913 Webster]

            Perhaps my God, though he be far before,
            May turn, and take me by the hand, and more
            May strengthen my decays.             --Herbert.
      [1913 Webster]

            His [Johnson's] failure was not to be ascribed to
            intellectual decay.                   --Macaulay.
      [1913 Webster]

            Which has caused the decay of the consonants to
            follow somewhat different laws.       --James Byrne.
      [1913 Webster]

   2. Destruction; death. [Obs.] --Spenser.
      [1913 Webster]

   3. Cause of decay. [R.]
      [1913 Webster]

            He that plots to be the only figure among ciphers,
            is the decay of the whole age.        --Bacon.

   Syn: Decline; consumption. See Decline.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Decay \De*cay"\, v. i. [imp. & p. p. Decayed; p. pr. & vb. n.
   Decaying.] [OF. decaeir, dechaer, decheoir, F. d['e]choir,
   to decline, fall, become less; L. de- + cadere to fall. See
   Chance.]
   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.
   [1913 Webster]

         Ill fares the land, to hastening ills a prey,
         Where wealth accumulates and men decay.  --Goldsmith.
   [1913 Webster]

WordNet (r) 3.0 (2006):

decay
    n 1: the process of gradually becoming inferior
    2: a gradual decrease; as of stored charge or current [syn:
       decay, decline]
    3: the organic phenomenon of rotting [syn: decay,
       decomposition]
    4: an inferior state resulting from the process of decaying;
       "the corpse was in an advanced state of decay"; "the house
       had fallen into a serious state of decay and disrepair"
    5: the spontaneous disintegration of a radioactive substance
       along with the emission of ionizing radiation [syn: decay,
       radioactive decay, disintegration]
    v 1: lose a stored charge, magnetic flux, or current; "the
         particles disintegrated during the nuclear fission process"
         [syn: disintegrate, decay, decompose]
    2: fall into decay or ruin; "The unoccupied house started to
       decay" [syn: decay, crumble, dilapidate]
    3: undergo decay or decomposition; "The body started to decay
       and needed to be cremated"

Moby Thesaurus II by Grady Ward, 1.0:

154 Moby Thesaurus words for "decay":
   ablate, ablation, atomization, atomize, atrophy, biodegradability,
   biodegradation, break down, break up, breakup, canker, caries,
   carrion, catalysis, catalyst, collapse, come apart, consume,
   contaminate, corrode, corrosion, corrupt, corruption, crack up,
   crumble, crumble into dust, crumbling, curdle, dandruff,
   debilitate, decadence, decline, decompose, decomposition, decrease,
   defile, degenerate, degeneration, degradability, degradation,
   deteriorate, deterioration, dialysis, dilapidate, dilapidation,
   diminish, disintegrate, disintegration, disjoin, disjunction,
   disorganization, disorganize, dissociation, dissolution, dissolve,
   downfall, dry rot, dwindle, ebb, enfeeble, erode, erosion,
   excrement, fading, failing, fall into decay, fall to pieces,
   ferment, fester, filth, fission, foul matter, foulness, furfur,
   gangrene, go bad, go off, go to pieces, go to pot, go to seed,
   hydrolysis, hydrolyst, incoherence, mess, mildew, mold, molder,
   mortification, mortify, mould, moulder, muck, mucus, necrose,
   necrosis, obscenity, ordure, oxidation, oxidization, perish,
   photolysis, pollute, pus, putrefaction, putrefy, putresce,
   putrescence, putrid matter, putridity, putridness, rancidity,
   rancidness, rankle, rankness, ravages of time, resolution, rot,
   rottenness, rotting, ruin, rust, sap, scurf, scuz, slime, slough,
   smut, snot, sordes, sour, sphacelate, sphacelation, sphacelus,
   split, splitting, spoil, spoilage, suppurate, taint, thermolysis,
   tooth decay, turn, undermine, wane, waste away, wasting, weaken,
   weakening, wear, wear and tear, wear away, wither, work, wreck



The Jargon File (version 4.4.7, 29 Dec 2003):

decay
 n.,vi

    [from nuclear physics] An automatic conversion which is applied to most
    array-valued expressions in C; they ?decay into? pointer-valued
    expressions pointing to the array's first element. This term is borderline
    techspeak, but is not used in the official standard for the language.


The Free On-line Dictionary of Computing (30 December 2018):

decay

   [Nuclear physics] An automatic conversion which is applied to
   most array-valued expressions in C; they "decay into"
   pointer-valued expressions pointing to the array's first
   element.  This term is not used in the official standard for
   the language.

   [Jargon File]