Source : Webster's Revised Unabridged Dictionary (1913)

Effloresce \Ef`flo*resce"\, v. i. [imp. & p. p. {Effloresced};
   p. pr. & vb. n. {Efflorescing}.] [L. efflorescere to bloom,
   blossom; ex + florescere to begin to blossom, incho., fr.
   florere to blossom, fr. flos a flower. See {Flower}.]
   1. To blossom forth. --Carlyle.

   2. (Chem.) To change on the surface, or throughout, to a
      whitish, mealy, or crystalline powder, from a gradual
      decomposition, esp. from the loss of water, on simple
      exposure to the air; as, Glauber's salts, and many others,
      effloresce.

   3. To become covered with a whitish crust or light
      crystallization, from a slow chemical change between some
      of the ingredients of the matter covered and an acid
      proceeding commonly from an external source; as, the walls
      of limestone caverns sometimes effloresce with nitrate of
      calcium in consequence of the action in consequence of
      nitric acid formed in the atmosphere.

Source : WordNet®

effloresce
     v 1: burst forth into or as if into flower; "These manifestations
          effloresced in the past" [syn: {burst forth}]
     2: assume crystalline form; become crystallized [syn: {crystallize},
         {crystalize}, {crystalise}]
     3: become encrusted with crystals due to evaporation