Source : Webster's Revised Unabridged Dictionary (1913)

Grief \Grief\ (gr[=e]f), n. [OE. grief, gref, OF. grief, gref,
   F. grief, L. gravis heavy; akin to Gr. bary`s, Skr. guru,
   Goth. ka['u]rus. Cf. {Barometer}, {Grave}, a., {Grieve},
   {Gooroo.}]
   1. Pain of mind on account of something in the past; mental
      suffering arising from any cause, as misfortune, loss of
      friends, misconduct of one's self or others, etc.; sorrow;
      sadness.

            The mother was so afflicted at the loss of a fine
            boy, . . . that she died for grief of it. --Addison.

   2. Cause of sorrow or pain; that which afficts or distresses;
      trial; grievance.

            Be factious for redress of all these griefs. --Shak.

   3. Physical pain, or a cause of it; malady. [R.]

            This grief (cancerous ulcers) hastened the end of
            that famous mathematician, Mr. Harriot. --Wood.

   {To come to grief}, to meet with calamity, accident, defeat,
      ruin, etc., causing grief; to turn out badly. [Colloq.]

   Syn: Affiction; sorrow; distress; sadness; trial; grievance.

   Usage: {Grief}, {Sorrow}, {Sadness}. Sorrow is the generic
          term; grief is sorrow for some definite cause -- one
          which commenced, at least, in the past; sadness is
          applied to a permanent mood of the mind. Sorrow is
          transient in many cases; but the grief of a mother for
          the loss of a favorite child too often turns into
          habitual sadness. ``Grief is sometimes considered as
          synonymous with sorrow; and in this case we speak of
          the transports of grief. At other times it expresses
          more silent, deep, and painful affections, such as are
          inspired by domestic calamities, particularly by the
          loss of friends and relatives, or by the distress,
          either of body or mind, experienced by those whom we
          love and value.'' --Cogan. See {Affliction}.

Source : WordNet®

grief
     n 1: intense sorrow caused by loss of a loved one (especially by
          death) [syn: {heartache}, {heartbreak}, {brokenheartedness}]
     2: something that causes great unhappiness; "her death was a
        great grief to John" [syn: {sorrow}]