Webster’s Revised Unabridged Dictionary · 1913
Diphtheria
Diph·the′ri·a, n. [NL., fr. Gr. διφθέρα leather (hence taken in the sense of membrane): cf. δέφειν to make soft, L. depsere to knead.] (Med.) A very dangerous contagious disease in which the air passages, and especially the throat, become coated with a false membrane, produced by the solidification of an inflammatory exudation. Cf. Group.