Source : Webster's Revised Unabridged Dictionary (1913)

Melancholia \Mel`an*cho"li*a\, n. [L. See {Melancholy}.] (Med.)
   A kind of mental unsoundness characterized by extreme
   depression of spirits, ill-grounded fears, delusions, and
   brooding over one particular subject or train of ideas.

Source : WordNet®

melancholia
     n : extreme depression characterized by tearful sadness and
         irrational fears