The Collaborative International Dictionary of English v.0.48:

Claimant \Claim"ant\, n. [Cf. OF. clamant, p. pr. of clamer. Cf.
   Clamant.]
   One who claims; one who asserts a right or title; a claimer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

claimant
    n 1: someone who claims a benefit or right or title; "claimants
         of unemployment compensation"; "he was a claimant to the
         throne"

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "claimant":
   accusant, accuser, allegator, appellant, applicant, aspirant,
   bidder, candidate, complainant, delator, impeacher, impugner,
   indictor, informer, libelant, party, petitioner, plaintiff,
   postulant, prosecutor, seeker, solicitant, solicitor, suitor,
   suppliant, supplicant, the prosecution



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

CLAIMANT. In the courts of admiralty, when the suit is in rem, the cause is
entitled in the Dame of the libellant against the thing libelled, as A B v.
Ten cases of calico and it preserves that title through the whole progress
of the suit.When a person is authorized and admitted to defend the libel, he
is called the claimant. The United States v. 1960 bags of coffee; 8 Cranch,
R. 398; United States v. The Mars; 8 Cranch, R. 417; 30 hhds. of sugar,
(Brentzon, claimant, v. Boyle. 9 Cranch, R. 191.