\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.