atresia (n.) Look up atresia at Dictionary.com
"occlusion of a natural passage in the body, absence of a natural opening or passage," 1807, from Modern Latin atresia, from Greek atretos "not perforated," from a- "not, without" (see a- (3)) + tresis "perforation," from PIE root *tere- (1) "to rub, turn," with derivatives referring to boring and drilling. Related: Atresic.