The Collaborative International Dictionary of English v.0.48:

Avow \A*vow"\, n. [Cf. F. aveu.]
   Avowal. [Obs.] --Dryden.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Avow \A*vow"\, v. t. & i. [OF. avouer, fr. LL. votare to vow,
   fr. L. votun. See Vote, n.]
   To bind, or to devote, by a vow. [Obs.] --Wyclif.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Avow \A*vow"\, n.
   A vow or determination. [Archaic]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Avow \A*vow"\, v. t. [imp. & p. p. Avowed (?); p. pr. & vb. n.
   Avowing.] [F. avouver, fr. L. advocare to call to (whence
   the meanings, to call upon as superior; recognize as lord,
   own, confess); ad + vocare to call. See Advocate,
   Avouch.]
   1. To declare openly, as something believed to be right; to
      own or acknowledge frankly; as, a man avows his principles
      or his crimes.
      [1913 Webster]

            Which I to be the of Israel's God
            Avow, and challenge Dagon to the test. --Milton.
      [1913 Webster]

   2. (Law) To acknowledge and justify, as an act done. See
      Avowry. --Blackstone.
      [1913 Webster]

   Syn: To acknowledge; own; confess. See Confess.
        [1913 Webster]

WordNet (r) 3.0 (2006):

avow
    v 1: to declare or affirm solemnly and formally as true; "Before
         God I swear I am innocent" [syn: affirm, verify,
         assert, avow, aver, swan, swear]
    2: admit openly and bluntly; make no bones about [syn: avow,
       avouch] [ant: disavow]

Moby Thesaurus II by Grady Ward, 1.0:

86 Moby Thesaurus words for "avow":
   accept, acknowledge, admit, admit everything, affirm,
   agree provisionally, allege, allow, announce, annunciate, argue,
   assent grudgingly, assert, assever, asseverate, attest, aver,
   avouch, bear witness, certify, claim, come clean, concede, confess,
   contend, cop a plea, declare, defend, depone, depose, disclose,
   enunciate, express, express general agreement, express the belief,
   give evidence, go along with, grant, have, hold, insist,
   issue a manifesto, lay down, let on, maintain, manifesto,
   not oppose, open up, out with it, own, own up, plead guilty,
   predicate, pretend, pretext, proclaim, profess, pronounce, protest,
   protest too much, purport, put, put it, recognize, say, set down,
   speak, speak out, speak up, spill, spill it, spit it out,
   stand for, stand on, state, submit, swear, tell all,
   tell the truth, testify, vindicate, vouch, vow, warrant, witness,
   yield



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

AVOW or ADVOW, practice. Signifies to justify or maintain an act formerly
done. For example, when replevin is brought for a thing distrained, and the
distrainer justifies the taking, he is said to avow. Termes de la Ley. This
word also signifies to bring forth anything. Formerly when a stolen thing
was found in the possession of any one" he was bound advocare, i. e. to
produce the seller from whom he alleged he had bought it, to justify the
sale, and so on till they found the thief. Afterwards the word was taken to
mean anything which a man admitted to be his own or done by him, and in this
sense it is mentioned in Fleta, lib. 1, c. 5, par 4. Cunn., Dict. h.t.