The Collaborative International Dictionary of English v.0.48:

Efflorescence \Ef`flo*res"cence\, n. [F. efflorescence.]
   1. (Bot.) Flowering, or state of flowering; the blooming of
      flowers; blowth.
      [1913 Webster]

   2. (Med.) A redness of the skin; eruption, as in rash,
      measles, smallpox, scarlatina, etc.
      [1913 Webster]

   3. (Chem.)
      (a) The formation of the whitish powder or crust on the
          surface of efflorescing bodies, as salts, etc.
      (b) The powder or crust thus formed.
          [1913 Webster]

WordNet (r) 3.0 (2006):

efflorescence
    n 1: the period of greatest prosperity or productivity [syn:
         flower, prime, peak, heyday, bloom, blossom,
         efflorescence, flush]
    2: any red eruption of the skin [syn: rash, roseola,
       efflorescence, skin rash]
    3: the time and process of budding and unfolding of blossoms
       [syn: blossoming, flowering, florescence,
       inflorescence, anthesis, efflorescence]
    4: a powdery deposit on a surface [syn: efflorescence,
       bloom]