[at.el.ec.ta.sis] n, pl -ta.ses [NL, fr. Gk ateles incomplete, defective (fr. a-
[2]a- + telos end) + ektasis extension, fr. ekteinein to stretch out, fr. ex- + teinein to stretch--more at telos, thin] (1859): collapse of the expanded lung; also: defective expansion of the pulmonary alveoli at birth