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]

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

WIDOW'S CHAMBER, Eng. law. In London the apparel of a widow and the
furniture of her chamber, left by her deceased husband, is so called, and
the widow is entitled to it. 2 Bl. Com. 518.