The Collaborative International Dictionary of English v.0.48:

Areola \A*re"o*la\, n.; pl. Areol[ae]. [L. areola, dim. of
   area: cf. F. ar['e]ole. See Area.]
   1. An interstice or small space, as between the cracks of the
      surface in certain crustaceous lichens; or as between the
      fibers composing organs or vessels that interlace; or as
      between the nervures of an insect's wing.
      [1913 Webster]

   2. (Anat. & Med.) The colored ring around the nipple, or
      around a vesicle or pustule.
      [1913 Webster]

WordNet (r) 3.0 (2006):

areola
    n 1: small space in a tissue or body part such as the area
         between veins on a leaf or an insect's wing
    2: small circular area such as that around the human nipple or
       an inflamed area around a pimple or insect bite [syn:
       areola, ring of color]