The Collaborative International Dictionary of English v.0.48:

Angelus \An"ge*lus\, n. [L.] (R. C. Ch.)
      (a) A form of devotion in which three Ave Marias are
          repeated. It is said at morning, noon, and evening, at
          the sound of a bell.
      (b) The Angelus bell. --Shipley.
          [1913 Webster]

WordNet (r) 3.0 (2006):

angelus
    n 1: the sound of a bell rung in Roman Catholic churches to
         announce the time when the Angelus should be recited [syn:
         angelus bell, angelus]
    2: a prayer said 3 times a day by Roman Catholics in memory of
       the Annunciation

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "Angelus":
   Angelus bell, Ave, Ave Maria, Hail Mary, Kyrie Eleison,
   Paternoster, aid prayer, alarm, alarum, appeal, battle cry,
   beadroll, beads, beseechment, bidding prayer, birdcall, breviary,
   bugle call, call, chaplet, collect, communion, contemplation,
   devotions, entreaty, grace, impetration, imploration, intercession,
   invocation, last post, litany, meditation, moose call, obsecration,
   obtestation, orison, petition, prayer, prayer wheel, rallying cry,
   rebel yell, reveille, rogation, rosary, silent prayer, suit,
   summons, supplication, taps, thanks, thanksgiving, trumpet call,
   war cry, whistle