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]

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "areola":
   O, annular muscle, annulus, aureole, chaplet, circle, circuit,
   circumference, circus, closed circle, corona, coronet, crown,
   cycle, diadem, discus, disk, eternal return, fairy ring, garland,
   glory, halo, lasso, logical circle, loop, looplet, magic circle,
   noose, orbit, radius, ring, rondelle, round, roundel, saucer,
   sphincter, vicious circle, wheel, wreath