Source : Webster's Revised Unabridged Dictionary (1913)

Parotitis \Par`o*ti"tis\, n. [NL. See {Parotid}, and {-itis}.]
   (Med.)
   Inflammation of the parotid glands.

   {Epidemic}, or {Infectious}, {parotitis}, mumps.

Epidemic \Ep`i*dem"ic\, Epidemical \Ep`i*dem"ic*al\, a. [L.
   epidemus, Gr. ?, ?, among the people, epidemic; ? in + ?
   people: cf. F. ['e]pid['e]mique. Cf. {Demagogue}.]
   1. (Med.) Common to, or affecting at the same time, a large
      number in a community; -- applied to a disease which,
      spreading widely, attacks many persons at the same time;
      as, an epidemic disease; an epidemic catarrh, fever, etc.
      See {Endemic}.

   2. Spreading widely, or generally prevailing; affecting great
      numbers, as an epidemic does; as, epidemic rage; an
      epidemic evil.

            It was the epidemical sin of the nation. --Bp.
                                                  Burnet.

Epidemic \Ep`i*dem"ic\, n. [Cf. {Epidemy}.]
   1. (Med.) An epidemic disease.

   2. Anything which takes possession of the minds of people as
      an epidemic does of their bodies; as, an epidemic of
      terror.

Source : WordNet®

epidemic
     n : a widespread outbreak of an infectious disease; many people
         are infected at the same time

epidemic
     adj : (especially of medicine) of disease or anything resembling a
           disease; attacking or affecting many individuals in a
           community or a population simultaneously; "an epidemic
           outbreak of influenza" [ant: {endemic}, {ecdemic}]