Definition of achalasia:
(n) :
(usually and especially) Such obstruction in the esophagus: esophageal achalasia.
(n) :
(medicine) A neuromuscular condition where a ring of muscles is unable to relax fully, causing obstruction of a lumen, as:
(n) :
(strictly) Such esophageal achalasia of primary (idiopathic) nature: primary esophageal achalasia.
(n) :
(occasionally) Such obstruction due to impairment of other gastrointestinal tract smooth muscles.