The Collaborative International Dictionary of English v.0.48:

Abandon \A*ban"don\ ([.a]*b[a^]n"d[u^]n), v. t. [imp. & p. p.
   Abandoned (-d[u^]nd); p. pr. & vb. n. Abandoning.] [OF.
   abandoner, F. abandonner; a (L. ad) + bandon permission,
   authority, LL. bandum, bannum, public proclamation,
   interdiction, bannire to proclaim, summon: of Germanic
   origin; cf. Goth. bandwjan to show by signs, to designate
   OHG. ban proclamation. The word meant to proclaim, put under
   a ban, put under control; hence, as in OE., to compel,
   subject, or to leave in the control of another, and hence, to
   give up. See Ban.]
   1. To cast or drive out; to banish; to expel; to reject.
      [Obs.]
      [1913 Webster]

            That he might . . . abandon them from him. --Udall.
      [1913 Webster]

            Being all this time abandoned from your bed. --Shak.
      [1913 Webster]

   2. To give up absolutely; to forsake entirely; to renounce
      utterly; to relinquish all connection with or concern on;
      to desert, as a person to whom one owes allegiance or
      fidelity; to quit; to surrender.
      [1913 Webster]

            Hope was overthrown, yet could not be abandoned.
                                                  --I. Taylor.
      [1913 Webster]

   3. Reflexively: To give (one's self) up without attempt at
      self-control; to yield (one's self) unrestrainedly; --
      often in a bad sense.
      [1913 Webster]

            He abandoned himself . . . to his favorite vice.
                                                  --Macaulay.
      [1913 Webster]

   4. (Mar. Law) To relinquish all claim to; -- used when an
      insured person gives up to underwriters all claim to the
      property covered by a policy, which may remain after loss
      or damage by a peril insured against.
      [1913 Webster]

   Syn: To give up; yield; forego; cede; surrender; resign;
        abdicate; quit; relinquish; renounce; desert; forsake;
        leave; retire; withdraw from.

   Usage: To Abandon, Desert, Forsake. These words agree
          in representing a person as giving up or leaving some
          object, but differ as to the mode of doing it. The
          distinctive sense of abandon is that of giving up a
          thing absolutely and finally; as, to abandon one's
          friends, places, opinions, good or evil habits, a
          hopeless enterprise, a shipwrecked vessel. Abandon is
          more widely applicable than forsake or desert. The
          Latin original of desert appears to have been
          originally applied to the case of deserters from
          military service. Hence, the verb, when used of
          persons in the active voice, has usually or always a
          bad sense, implying some breach of fidelity, honor,
          etc., the leaving of something which the person should
          rightfully stand by and support; as, to desert one's
          colors, to desert one's post, to desert one's
          principles or duty. When used in the passive, the
          sense is not necessarily bad; as, the fields were
          deserted, a deserted village, deserted halls. Forsake
          implies the breaking off of previous habit,
          association, personal connection, or that the thing
          left had been familiar or frequented; as, to forsake
          old friends, to forsake the paths of rectitude, the
          blood forsook his cheeks. It may be used either in a
          good or in a bad sense.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Abandon \A`ban`don"\ ([.a]`b[aum]N`d[^o]N"), n. [F. See
   Abandon.]
   A complete giving up to natural impulses; freedom from
   artificial constraint; careless freedom or ease.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Abandon \A*ban"don\, n. [F. abandon. fr. abandonner. See
   Abandon, v.]
   Abandonment; relinquishment. [Obs.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

abandon
    n 1: the trait of lacking restraint or control; reckless freedom
         from inhibition or worry; "she danced with abandon" [syn:
         abandon, wantonness, unconstraint]
    2: a feeling of extreme emotional intensity; "the wildness of
       his anger" [syn: wildness, abandon]
    v 1: forsake, leave behind; "We abandoned the old car in the
         empty parking lot"
    2: give up with the intent of never claiming again; "Abandon
       your life to God"; "She gave up her children to her ex-
       husband when she moved to Tahiti"; "We gave the drowning
       victim up for dead" [syn: abandon, give up]
    3: leave behind empty; move out of; "You must vacate your office
       by tonight" [syn: vacate, empty, abandon]
    4: stop maintaining or insisting on; of ideas or claims; "He
       abandoned the thought of asking for her hand in marriage";
       "Both sides have to give up some claims in these
       negotiations" [syn: abandon, give up]
    5: leave someone who needs or counts on you; leave in the lurch;
       "The mother deserted her children" [syn: abandon,
       forsake, desolate, desert]

Moby Thesaurus II by Grady Ward, 1.0:

346 Moby Thesaurus words for "abandon":
   abandonment, abjection, abjure, abort, abscond, acknowledge defeat,
   ardency, ardor, back out, beat a retreat, beg a truce, beg off,
   belay, boundlessness, bow out, break the habit, brush aside,
   brush off, cancel, capitulate, careless abandon, carelessness,
   cast, cast aside, cast away, cast off, casualness, cease, cede,
   chuck, come to terms, commitment, committedness, corruptedness,
   corruption, corruptness, craze, cry off, cry pax, cry quits,
   cursoriness, cut, cut it out, debasement, decadence, decadency,
   dedication, deep-six, degeneracy, degenerateness, degeneration,
   degradation, delirium, demoralization, depart from, depravation,
   depravedness, depravity, desert, desist, devotedness, devotion,
   devoutness, disappear, discard, discontinue, disgorge, dismiss,
   dispense with, dispose of, disregardfulness, dissoluteness, disuse,
   ditch, do without, drop, drop it, drop out, drop the subject, dump,
   earnestness, ease, easiness, ecstasy, egregiousness, eighty-six,
   eliminate, end, enormousness, evacuate, exaggeration, excess,
   excessiveness, exorbitance, exorbitancy, extravagance,
   extravagancy, extreme, extremes, extremism, extremity, exuberance,
   fabulousness, faith, faithfulness, fervency, fervidness, fervor,
   fidelity, fire, fire and fury, forget, forget about it, forget it,
   forgetfulness, forgo, forsake, forswear, freedom, frenzy, fun,
   furor, furore, fury, games, get along without, get quit of,
   get rid of, get shut of, giantism, gigantism, give away, give over,
   give up, gluttony, go back on, goldbrick, goof off, halt,
   hand over, hastiness, have done with, heartiness, heat, heatedness,
   heedlessness, hold, hyperbole, hypertrophy, hysteria, immoderacy,
   immoderateness, immoderation, impassionedness, implore mercy,
   impulsiveness, inconsiderateness, inconsideration, incontinence,
   indifference, indiscipline, inordinacy, inordinance,
   inordinateness, insouciance, intemperance, intemperateness,
   intensity, intentness, intoxication, irrepressibility, jettison,
   jilt, jump, junk, kick, kiss good-bye, knock it off,
   lack of foresight, laxity, laxness, lay aside, lay off, laziness,
   leave, leave behind, leave flat, leave loose ends, leave off,
   leave undone, let alone, let be, let dangle, let go, let it go,
   let slip, liberty, license, licentiousness, looseness, loyalty,
   madness, make a sacrifice, malinger, maroon, miss, monstrousness,
   moral pollution, moral turpitude, naturalness, nimiety,
   noncoercion, nonintimidation, oblivion, offhandedness, omit,
   orgasm, orgy, outrageousness, overdevelopment, overgreatness,
   overgrowth, overindulgence, overlargeness, overmuch, overmuchness,
   part with, pass over, pass up, passion, passionateness,
   perfunctoriness, permissiveness, play, pray for quarter, pretermit,
   procrastinate, profligacy, pull out, push aside, put aside, quit,
   quit cold, quitclaim, radicalism, rage, rapture, ravishment,
   recant, recklessness, refrain, regardlessness, reject, relinquish,
   remove, render up, renege, renounce, reprobacy, repudiate, resign,
   resolution, retire, retract, retreat, riotousness, rottenness,
   run out on, sacrifice, say goodbye to, say uncle, scrap, scrub,
   seriousness, set aside, shake, shirk, shrug off, sincerity, skip,
   slack, slough, sneeze at, spare, spirit, spontaneity, sport,
   sprezzatura, stand down, stay, stop, surrender, swear off,
   tactlessness, take leave of, take the pledge, tearing passion,
   terminate, think nothing of, thoughtlessness, throw away,
   throw off, throw out, throw over, throw overboard, throw up,
   thrust aside, too much, too-muchness, toss overboard,
   towering rage, transport, trifle, turn away from, turn up,
   turpitude, unconscionableness, unconstrained, unconstraint,
   uncontrol, undueness, unheedfulness, uninhibitedness,
   unmindfulness, unpreparedness, unreadiness, unreasonableness,
   unreserve, unrestrainedness, unrestraint, unruliness,
   unsolicitousness, unsolicitude, unstrictness, unthinkingness,
   vacate, vanish, vehemence, waive, wantonness, warmth, wildness,
   withdraw, yield, yield the palm, zeal