Source : Webster's Revised Unabridged Dictionary (1913)

Sclerotium \Scle*ro"ti*um\, n.; pl. {Sclerotia}. [NL., fr. Gr.
   sklhro`s hard.]
   1. (Bot.) A hardened body formed by certain fungi, as by the
      {Claviceps purpurea}, which produces ergot.

   2. (Zo["o]l.) The mature or resting stage of a plasmodium.

Source : WordNet®

Sclerotium
     n 1: form genus of sterile imperfect fungi; many form sclerotia;
          some cause sclerotium disease in plants [syn: {genus
          Sclerotium}]
     2: compact usually dark-colored mass of hardened mycelium
        constituting a vegetative food-storage body in various
        true fungi; detaches when mature and can give rise to new
        growth