Source : Webster's Revised Unabridged Dictionary (1913)

Deserter \De*sert"er\ (?), n.
   One who forsakes a duty, a cause or a party, a friend, or any
   one to whom he owes service; especially, a soldier or a
   seaman who abandons the service without leave; one guilty of
   desertion.

Source : WordNet®

deserter
     n 1: a disloyal person who betrays or deserts his cause or
          religion or political party or friend etc. [syn: {apostate},
           {renegade}, {turncoat}, {recreant}, {ratter}]
     2: a person who abandons their duty (as on a military post)
        [syn: {defector}]