The Collaborative International Dictionary of English v.0.48:

Credo \Cre"do\ (kr?"d?), n. [L. See Creed.]
   The creed, as sung or read in the Roman Catholic church.
   [1913 Webster]

         He repeated Aves and Credos.             --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

credo
    n 1: any system of principles or beliefs [syn: creed, credo]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "Credo":
   Agnus Dei, Alleluia, Anamnesis, Blessing, Canon, Collect,
   Communion, Consecration, Dismissal, Epistle, Fraction, Gloria,
   Gospel, Gradual, Introit, Kyrie, Kyrie Eleison, Last Gospel,
   Lavabo, Offertory, Paternoster, Pax, Post-Communion, Preface,
   Sanctus, Secreta, Tersanctus, Tract



Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "credo":
   Athanasian Creed, Catechism, Nicene Creed, Weltanschauung,
   articles of faith, articles of religion, belief, catechism,
   credenda, creed, cult, doctrinal statement, doctrine, dogma, faith,
   formulated belief, gospel, ideology, ism, orthodoxy,
   political faith, political philosophy, religion, religious belief,
   religious faith, school, system of belief, system of beliefs,
   teaching, theology, tradition, weltanschauung, world view