pleura

from The Century Dictionary.

• noun Plural of pleuron.
• The principal serous membrane of the thorax; the shut sac, having a serous surface, which lines the walls of the chest, and is reflected over the surface of each lung.
• In conchology, one of the lateral tracts on each side of the rachis of the lingual ribbon of the odontophore: generally used in the plural.
• In comparative anatomy, the lateral portion of one of the rings composing the integument of an arthropod or articulate animal, lying between the tergum and sternum, and in insects and crustaceans consisting of two pieces, the epimeron and episternum.
• All the parts of the pleura except the pulmonary portion.

from the GNU version of the Collaborative International Dictionary of English.

• noun pl. of pleuron.
• noun The smooth serous membrane which closely covers the lungs and the adjacent surfaces of the thorax; the pleural membrane.
• noun The closed sac formed by the pleural membrane about each lung, or the fold of membrane connecting each lung with the body wall.
• noun (Zoöl.) Same as Pleuron.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun anatomy The smooth serous membrane which closely covers the lungs and the adjacent surfaces of the thorax; the pleural membrane.
• noun Plural form of pleuron.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the thin serous membrane around the lungs and inner walls of the chest