Pleura

Definition:

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

Compare pleura with other words:

pleura vs. pleurae