anaphylaxis /(ăn`ȧ*fī*lăk"sĭs or ăn`ȧ*fĭ*lăk"sĭs)/

an·a·phy·lax·is

anaphylaxis

n.
  1. Hypersensitivity (to a foreign antigen) resulting from prior contact with the same or a related substance. (Med.)
  2. An immediate but transient systemic reaction to an antigenic substance to which a person has become hypersensitized; it is characterized by the contraction of smooth muscle and capillary dilation. (Med.)
  3. Anaphylactic shock. (Med)