1. Total or partial collapse of the lung.
2. A congenital condition characterized by the incomplete expansion of the lungs at birth.

[New Latin : Greek atelēs, incomplete (a-, not; see a-¹ + telos, end; see telo-) + Greek ektasis, stretching out (from ekteinein, to stretch out : ek-, out; see ecto- + teinein, to stretch; see epitasis).]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.