The Collaborative International Dictionary of English v.0.48:

Retting \Ret"ting\, n.
   1. The act or process of preparing flax for use by soaking,
      maceration, and kindred processes; -- also called
      rotting. See Ret. --Ure.
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   2. A place where flax is retted; a rettery. --Ure.
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The Collaborative International Dictionary of English v.0.48:

Rot \Rot\, v. i. [imp. & p. p. Rotted; p. pr. & vb. n.
   Rotting.] [OE. rotien, AS. rotian; akin to D. rotten, Prov.
   G. rotten, OHG. rozz?n, G. r["o]sten to steep flax, Icel.
   rotna to rot, Sw. ruttna, Dan. raadne, Icel. rottin rotten.
   [root]117. Cf. Ret, Rotten.]
   1. To undergo a process common to organic substances by which
      they lose the cohesion of their parts and pass through
      certain chemical changes, giving off usually in some
      stages of the process more or less offensive odors; to
      become decomposed by a natural process; to putrefy; to
      decay.
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            Fixed like a plant on his peculiar spot,
            To draw nutrition, propagate, and rot. --Pope.
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   2. Figuratively: To perish slowly; to decay; to die; to
      become corrupt.
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            Four of the sufferers were left to rot in irons.
                                                  --Macaulay.
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            Rot, poor bachelor, in your club.     --Thackeray.
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   Syn: To putrefy; corrupt; decay; spoil.
        [1913 Webster]

WordNet (r) 3.0 (2006):

rotting
    n 1: (biology) the process of decay caused by bacterial or
         fungal action [syn: decomposition, rot, rotting,
         putrefaction]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "rotting":
   bad, cankered, carious, corrupt, decayed, decomposed, festering,
   foul, gangrened, gangrenous, gone bad, mortified, necrosed,
   necrotic, peccant, putrefacient, putrefactive, putrefied,
   putrescent, putrid, rotten, saprobic, saprogenic, saprogenous,
   saprophilous, saprophytic, septic, sphacelated, spoiled,
   suppurating, suppurative, ulcerated