The Collaborative International Dictionary of English v.0.48:

Vow \Vow\, v. i.
   To make a vow, or solemn promise.
   [1913 Webster]

         Better is it that thou shouldest not vow, than that
         thou shouldest vow and not pay.          --Eccl. v. 5.
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The Collaborative International Dictionary of English v.0.48:

Vow \Vow\, n. [OE. vou, OF. vou, veu, vo, vu, F. v?u, from L.
   votum, from vovere, to vow. Cf. Avow, Devout, Vote.]
   [1913 Webster]
   1. A solemn promise made to God, or to some deity; an act by
      which one consecrates or devotes himself, absolutely or
      conditionally, wholly or in part, for a longer or shorter
      time, to some act, service, or condition; a devotion of
      one's possessions; as, a baptismal vow; a vow of poverty.
      "Nothing . . . that may . . . stain my vow of Nazarite."
      --Milton.
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            I pray thee, let me go and pay my vow. --2 Sam. xv.
                                                  7.
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            I am combined by a sacred vow.        --Shak.
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   2. Specifically, a promise of fidelity; a pledge of love or
      affection; as, the marriage vow.
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            Knights of love, who never broke their vow;
            Firm to their plighted faith.         --Dryden.
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The Collaborative International Dictionary of English v.0.48:

Vow \Vow\, v. t. [imp. & p. p. Vowed; p. pr. & vb. n.
   Vowing.] [OE. vouen, OF. vouer, voer, F. vouer, LL. votare.
   See Vow, n.]
   [1913 Webster]
   1. To give, consecrate, or dedicate to God, or to some deity,
      by a solemn promise; to devote; to promise solemnly. "When
      thou vowest a vow unto God, defer not to pay it." --Eccl.
      v. 4.
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            [Men] that vow a long and weary pilgrimage. --Shak.
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   2. To assert solemnly; to asseverate.
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WordNet (r) 3.0 (2006):

vow
    n 1: a solemn pledge (to oneself or to another or to a deity) to
         do something or to behave in a certain manner; "they took
         vows of poverty"
    v 1: make a vow; promise; "He vowed never to drink alcohol
         again"
    2: dedicate to a deity by a vow [syn: vow, consecrate]