The Collaborative International Dictionary of English v.0.48:

Desertion \De*ser"tion\ (d[-e]*z[~e]r"sh[u^]n), n. [L. desertio:
   cf. F. d['e]sertion.]
   1. The act of deserting or forsaking; abandonment of a
      service, a cause, a party, a friend, or any post of duty;
      the quitting of one's duties willfully and without right;
      esp., an absconding from military or naval service.
      [1913 Webster]

            Such a resignation would have seemed to his superior
            a desertion or a reproach.            --Bancroft.
      [1913 Webster]

   2. The state of being forsaken; desolation; as, the king in
      his desertion.
      [1913 Webster]

   3. Abandonment by God; spiritual despondency.
      [1913 Webster]

            The spiritual agonies of a soul under desertion.
                                                  --South.
      [1913 Webster]

WordNet (r) 3.0 (2006):

desertion
    n 1: withdrawing support or help despite allegiance or
         responsibility; "his abandonment of his wife and children
         left them penniless" [syn: desertion, abandonment,
         defection]
    2: the act of giving something up [syn: abandonment,
       forsaking, desertion]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "desertion":
   AWOL, French leave, abandonment, absence without leave,
   absquatulation, apostasy, atheism, backsliding, betrayal, bolt,
   breakaway, crossing-over, decampment, defection, defenselessness,
   degeneration, dereliction, deserter, desolation, disappearance,
   disappearing act, disloyalty, elopement, exit, faithlessness,
   fall from grace, fatherlessness, flight, forlornness, fugitation,
   going over, hasty retreat, hegira, helplessness, homelessness,
   impiety, impiousness, irreligion, irreverence, kithlessness, lapse,
   lapse from grace, motherlessness, quick exit, ratting,
   recidivation, recidivism, recreancy, renunciation, running away,
   schism, scramming, secession, skedaddle, skedaddling, treason,
   turning traitor, undutifulness, walkout



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

DESERTION, crim. law. An offence which consists in the abandonment of the
public service, in the army or navy, without leave.
     2. The Act of March 16, 1802, s. 19, enacts, that if any non-
commissioned officer, musician, or private, shall desert the service of the
United States, he shall, in addition to the penalties mentioned in the rules
and articles of war, be liable to serve for and during such period as shall,
with the time he may have served previous to his desertion, amount to the
full term of his enlistment; and such soldier shall and may be tried by a
court-martial, and punished, although the term of his enlistment may have
elapsed previous to his being apprehended or tried.
     3. By the articles of war, it is enacted, that "any non-commissioned
officer or soldier who shall, without leave from his commanding officer,
absent himself from his troop, company, or detachment, shall, upon being
convicted thereof, be punished, according to the nature of his offence, at
the discretion of a court-martial." Art. 21.
     4. By the articles for the government of the navy, art. 16, it is
enacted, that "if any person in the navy shall desert to an enemy, or rebel,
he shall suffer death;" and by art. 17, "if any person in the navy shall
desert, or shall entice others to desert, he shall suffer death, or such
other punishment as a court-martial shall adjudge."



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

DESERTION, torts. The act by which a man abandons his wife and children, or
either of them.
     2. On proof of desertion, the courts possess the power to grant the
'Wife, or such children as have been deserted, alimony (q.v.)



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

DESERTION, MALICIOUS. The act of a husband or wife, in leaving a consort,
without just cause, for the purpose of causing a perpetual separation. Vide
Abandonment, malicious.