The Collaborative International Dictionary of English v.0.48:

Avow \A*vow"\, n. [Cf. F. aveu.]
   Avowal. [Obs.] --Dryden.
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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.
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The Collaborative International Dictionary of English v.0.48:

Avow \A*vow"\, n.
   A vow or determination. [Archaic]
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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.
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            Which I to be the of Israel's God
            Avow, and challenge Dagon to the test. --Milton.
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   2. (Law) To acknowledge and justify, as an act done. See
      Avowry. --Blackstone.
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   Syn: To acknowledge; own; confess. See Confess.
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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