atelectasis
noun
at·el·ec·ta·sis ˌa-tə-ˈlek-tə-səs 
plural atelectases ˌa-tə-ˈlek-tə-ˌsēz
: collapse of the expanded lung
also : defective expansion of the pulmonary alveoli at birth
Word History
Etymology
borrowed from New Latin (in the phrase atelectasis pulmonum "incomplete dilatation of the lungs"), from Greek atelḗs "incomplete, unsuccessful" (from a- a- entry 2 + -telēs, adjective derivative of télos "fulfillment, completion, goal") + New Latin ectasis "expansion of a hollow or tubular organ, dilatation," borrowed from Greek éktasis "stretching out, extension" (action noun from ekteínein "to stretch out, extend"), from ek- ec- + tásis "stretching, tension" — more at telos, tenant entry 1
Note: The term was introduced by the German physician Eduard Jörg in De morbo pulmonum organico ex respiratione neonatorum imperfecta orto (Leipzig, 1832).
First Known Use
1837, in the meaning defined above
Medical Definition
atelectasis
noun
at·el·ec·ta·sis ˌat-ᵊl-ˈek-tə-səs
plural atelectases -ˌsēz
: collapse of the expanded lung
also : defective expansion of the pulmonary alveoli at birth