The Collaborative International Dictionary of English v.0.48:

Avail \A*vail"\, n.
   1. Profit; advantage toward success; benefit; value; as,
      labor, without economy, is of little avail.
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            The avail of a deathbed repentance.   --Jer. Taylor.
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   2. pl. Proceeds; as, the avails of a sale by auction.
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            The avails of their own industry.     --Stoddard.
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   Syn: Use; benefit; utility; profit; service.
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The Collaborative International Dictionary of English v.0.48:

Avail \A*vail"\, v. t. [imp. & p. p. Availed (?); p. pr. & vb.
   n. Availing.] [OE. availen, fr. F. ? (L. ad) + valoir to be
   worth, fr. L. valere to be strong, to be worth. See
   Valiant.]
   1. To turn to the advantage of; to be of service to; to
      profit; to benefit; to help; as, artifices will not avail
      the sinner in the day of judgment.
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            O, what avails me now that honor high ! --Milton.
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   2. To promote; to assist. [Obs.] --Pope.
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   To avail one's self of, to make use of; take advantage of.
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            Then shall they seek to avail themselves of names.
                                                  --Milton.
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            I have availed myself of the very first opportunity.
                                                  --Dickens.
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The Collaborative International Dictionary of English v.0.48:

Avail \A*vail"\, v. t. & i.
   See Avale, v. [Obs.] --Spenser.
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The Collaborative International Dictionary of English v.0.48:

Avail \A*vail"\, v. i.
   To be of use or advantage; to answer the purpose; to have
   strength, force, or efficacy sufficient to accomplish the
   object; as, the plea in bar must avail, that is, be
   sufficient to defeat the suit; this scheme will not avail;
   medicines will not avail to check the disease. "What signs
   avail ?" --Milton.
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         Words avail very little with me, young man. --Sir W.
                                                  Scott.
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WordNet (r) 3.0 (2006):

avail
    n 1: a means of serving; "of no avail"; "there's no help for it"
         [syn: avail, help, service]
    v 1: use to one's advantage; "He availed himself of the
         available resources"
    2: be of use to, be useful to; "It will avail them to dispose of
       their booty"
    3: take or use; "She helped herself to some of the office
       supplies" [syn: avail, help]

Moby Thesaurus II by Grady Ward, 1.0:

105 Moby Thesaurus words for "avail":
   abet, account, advance, advantage, aid, answer, applicability,
   appositeness, appropriateness, assist, bail out, be equal to,
   be handy, be of use, bear, bear a hand, befriend, behalf, behoof,
   benefit, benison, bestead, blessing, boon, break no bones, comfort,
   convenience, do, do good, do it, do no harm, do the trick, doctor,
   ease, favor, fill, fill the bill, fitness, fulfill, gain, get by,
   give a boost, give a hand, give a lift, give good returns,
   give help, go around, good, hack it, help, hold, interest, just do,
   lend a hand, lend one aid, make the grade, meet, meet requirements,
   pass, pass muster, pay, pay off, percentage, point, proffer aid,
   profit, protect, qualify, rally, reach, reclaim, redeem, relevance,
   relieve, remedy, render assistance, rescue, restore, resuscitate,
   revive, satisfy, save, serve, serve the purpose, service,
   serviceability, set up, stand, stand up, stretch, succor, suffice,
   suitability, take in tow, take it, use, usefulness, value, welfare,
   well-being, work, work for, world of good, worth, yield a profit



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

AVAIL. Profits of land; hence tenant paravail is one in actual possession,
who makes avail or profits of the land. Ham. N. P. 393.