The Collaborative International Dictionary of English v.0.48:

Emaciation \E*ma`ci*a"tion\, n. [Cf. F. ['e]maciation.]
   1. The act of making very lean.
      [1913 Webster]

   2. The state of being emaciated or reduced to excessive
      leanness; an excessively lean condition.
      [1913 Webster]

WordNet (r) 3.0 (2006):

emaciation
    n 1: extreme leanness (usually caused by starvation or disease)
         [syn: bonyness, boniness, emaciation, gauntness,
         maceration]