Webster's Revised Unabridged Dictionary · 1913

Diphtheria

Diphtheria , noun

[New Latin, from Greek {not transcribed} leather (hence taken in the sense of membrane): compare {not transcribed} to make soft, Latin depsere to knead.]

(Medicine) 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. Compare Group.