The Collaborative International Dictionary of English v.0.48:

Insolation \In`so*la"tion\, n. [L. insolatio: cf. F.
   insolation.]
   [1913 Webster]
   1. The act or process to exposing to the rays of the sun for
      the purpose of drying or maturing, as fruits, drugs, etc.,
      or of rendering acid, as vinegar.
      [1913 Webster]

   2. (Med.)
      (a) A sunstroke.
      (b) Exposure of a patient to the sun's rays; a sun bath.
          [1913 Webster]

   3. (Meteorology) The amount of sunlight impinging on the
      Earth's surface.
      [PJC]

WordNet (r) 3.0 (2006):

insolation
    n 1: sudden prostration due to exposure to the sun or excessive
         heat [syn: sunstroke, insolation, thermic fever,
         siriasis]
    2: incident solar radiation
    3: therapeutic exposure to sunlight [syn: heliotherapy,
       insolation]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "insolation":
   air-drying, anhydration, calefaction, calenture, cooking,
   coup de soleil, dehumidification, dehydration, desiccation,
   dielectric heating, drainage, drying, drying up, electric heating,
   electronic heating, evaporation, furnace heating, gas heating,
   heat exchange, heat prostration, heating, hot-air heating,
   increase of temperature, induction heating, mummification,
   oil heating, panel heating, radiant heating, recalescence,
   steam heating, sunstroke, superheating, tepefaction, thermic fever,
   torrefaction, warming, withering