Source : Webster's Revised Unabridged Dictionary (1913)

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}.

Source : WordNet®

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

pleurae
     See {pleura}

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