The Collaborative International Dictionary of English v.0.48:

Widow \Wid"ow\ (w[i^]d"[-o]), n. [OE. widewe, widwe, AS.
   weoduwe, widuwe, wuduwe; akin to OFries. widwe, OS. widowa,
   D. weduwe, G. wittwe, witwe, OHG. wituwa, witawa, Goth.
   widuw[=o], Russ. udova, OIr. fedb, W. gweddw, L. vidua, Skr.
   vidhav[=a]; and probably to Skr. vidh to be empty, to lack;
   cf. Gr. "hi`qeos a bachelor. [root]248. Cf. Vidual.]
   A woman who has lost her husband by death, and has not
   married again; one living bereaved of a husband. "A poor
   widow." --Chaucer.
   [1913 Webster]

   2. (Card Playing) In various games (such as "hearts"), any
      extra hand or part of a hand, as one dealt to the table.
      It may be taken by one of the players under certain
      circumstances.
      [Webster 1913 Suppl.]

   Grass widow. See under Grass.

   Widow bewitched, a woman separated from her husband; a
      grass widow. [Colloq.]

   Widow-in-mourning (Zool.), the macavahu.

   Widow monkey (Zool.), a small South American monkey
      (Callithrix lugens); -- so called on account of its
      color, which is black except the dull whitish arms, neck,
      and face, and a ring of pure white around the face.

   Widow's chamber (Eng. Law), in London, the apparel and
      furniture of the bedchamber of the widow of a freeman, to
      which she was formerly entitled.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Widow \Wid"ow\, a.
   Widowed. "A widow woman." --1 Kings xvii. 9. "This widow
   lady." --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Widow \Wid"ow\, v. t. [imp. & p. p. Widowed; p. pr. & vb. n.
   Widowing.]
   [1913 Webster]
   1. To reduce to the condition of a widow; to bereave of a
      husband; -- rarely used except in the past participle.
      [1913 Webster]

            Though in thus city he
            Hath widowed and unchilded many a one,
            Which to this hour bewail the injury. --Shak.
      [1913 Webster]

   2. To deprive of one who is loved; to strip of anything
      beloved or highly esteemed; to make desolate or bare; to
      bereave.
      [1913 Webster]

            The widowed isle, in mourning,
            Dries up her tears.                   --Dryden.
      [1913 Webster]

            Tress of their shriveled fruits
            Are widowed, dreary storms o'er all prevail. --J.
                                                  Philips.
      [1913 Webster]

            Mourn, widowed queen; forgotten Sion, mourn.
                                                  --Heber.
      [1913 Webster]

   3. To endow with a widow's right. [R.] --Shak.
      [1913 Webster]

   4. To become, or survive as, the widow of. [Obs.]
      [1913 Webster]

            Let me be married to three kings in a forenoon, and
            widow
            them all.                             --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

widow
    n 1: a woman whose husband is dead especially one who has not
         remarried [syn: widow, widow woman]
    v 1: cause to be without a spouse; "The war widowed many women
         in the former Yugoslavia"

Bouvier's Law Dictionary, Revised 6th Ed (1856):

WIDOW. An unmarried woman whose husband is dead.
     2. In legal writings, widow is an addition given to a woman who is
unmarried and whose husband is dead. The addition of spinster is given to a
woman who never was married. Lovel. on Wills, 269. See Addition. As to the
rights of a widow, seq Dower.



The Devil's Dictionary (1881-1906):

WIDOW, n.  A pathetic figure that the Christian world has agreed to
take humorously, although Christ's tenderness towards widows was one
of the most marked features of his character.