atresia

from WordNet (r) 3.0 (2006)

atresia
    n 1: an abnormal condition in which a normal opening or tube in
         the body (as the urethra) is closed or absent

from The Collaborative International Dictionary of English v.0.48

Atresia \A*tre"si*a\, n. [NL., fr. Gr. ? not perforated.] (Med.)
   Absence or closure of a natural passage or channel of the
   body; imperforation.
   [1913 Webster]