Source : Webster's Revised Unabridged Dictionary (1913)

Measles \Mea"sles\, n.; pl. in form, but used as singular in
   senses 1, 2, & 3. [D. mazelen; akin to G. masern, pl., and E.
   mazer, and orig. meaning, little spots. See {Mazer}.]
   1. (Med.) A contagious febrile disorder commencing with
      catarrhal symptoms, and marked by the appearance on the
      third day of an eruption of distinct red circular spots,
      which coalesce in a crescentic form, are slightly raised
      above the surface, and after the fourth day of the
      eruption gradually decline; rubeola.

            Measles commences with the ordinary symptoms of
            fever.                                --Am. Cyc.

Measles \Mea"sles\, n. [From lst {Measle}.]
   Leprosy; also, a leper. [Obs.]

Source : WordNet®

measles
     n : an acute and highly contagious viral disease marked by
         distinct red spots followed by a rash; occurs primarily
         in children [syn: {rubeola}, {morbilli}]