The Collaborative International Dictionary of English v.0.48:

Entreaty \En*treat"y\, n.; pl. Entreaties.
   1. Treatment; reception; entertainment. [Obs.] --B. Jonson.
      [1913 Webster]

   2. The act of entreating or beseeching; urgent prayer;
      earnest petition; pressing solicitation.
      [1913 Webster]

            Fair entreaty, and sweet blandishment. --Spenser.

   Syn: Solicitation; request; suit; supplication; importunity.
        [1913 Webster]

WordNet (r) 3.0 (2006):

entreaty
    n 1: earnest or urgent request; "an entreaty to stop the
         fighting"; "an appeal for help"; "an appeal to the public
         to keep calm" [syn: entreaty, prayer, appeal]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "entreaty":
   Angelus, Ave, Ave Maria, Hail Mary, Kyrie Eleison, Paternoster,
   adjuration, aid prayer, appeal, application, beadroll, beads,
   beseechment, bid, bidding prayer, breviary, call, chaplet, clamor,
   collect, communion, contemplation, cry, devotions, grace,
   impetration, imploration, imploring, imprecation, intercession,
   invocation, invocatory plea, litany, meditation, obsecration,
   obtestation, orison, petition, plea, prayer, prayer wheel,
   rogation, rosary, silent prayer, suit, supplication, thanks,
   thanksgiving