Source : Webster's Revised Unabridged Dictionary (1913)

Pleura \Pleu"ra\, n.,
   pl. of {Pleuron}.

Pleura \Pleu"ra\, n.; pl. L. {Pleur[ae]}, E. {Pleuras}. [NL., n.
   fem., fr. Gr. ? a rib, the side.]
   1. (Anat.)
      (a) The smooth serous membrane which closely covers the
          lungs and the adjacent surfaces of the thorax; the
          pleural membrane.
      (b) The closed sac formed by the pleural membrane about
          each lung, or the fold of membrane connecting each
          lung with the body wall.

   2. (Zo["o]l.) Same as {Pleuron}.

Pleuron \Pleu"ron\, n.; pl. {Pleura}. [NL., fr. Gr. ? a rib.]
   (Zo["o]l.)
   (a) One of the sides of an animal.
   (b) One of the lateral pieces of a somite of an insect.
   (c) One of lateral processes of a somite of a crustacean.

Source : WordNet®

pleura
     n : the thin serous membrane around the lungs and inner walls of
         the chest
     [also: {pleurae} (pl)]

pleura
     See {pleuron}
     [also: {pleurae} (pl)]