The Collaborative International Dictionary of English v.0.48:

Exfoliate \Ex*fo"li*ate\, v. i. [imp. & p. p. Exfoliated; p.
   pr. & vb. n. Exfoliating.] [L. exfoliare to strip of
   leaves; ex out, from + folium leaf.]
   1. To separate and come off in scales or lamin[ae], as pieces
      of carious bone or of bark.
      [1913 Webster]

   2. (Min.) To split into scales, especially to become
      converted into scales at the result of heat or
      decomposition.
      [1913 Webster]