The Collaborative International Dictionary of English v.0.48:

Secularism \Sec"u*lar*ism\, n.
   1. The state or quality of being secular; a secular spirit;
      secularity.
      [1913 Webster]

   2. The tenets or principles of the secularists.
      [1913 Webster]

WordNet (r) 3.0 (2006):

secularism
    n 1: a doctrine that rejects religion and religious
         considerations

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "secularism":
   Buddhology, Mariolatry, Mariology, Marxism, Mercersburg theology,
   animalism, apologetics, atheism, atomism, behaviorism, canonics,
   commonsense realism, crisis theology, dialectical materialism,
   dialogical theology, disbelief, divinity, doctrinalism, doctrinism,
   dogmatics, down-to-earthness, earthiness, earthliness, empiricism,
   epiphenomenalism, eschatology, existential theology, faithlessness,
   freedom from illusion, hagiography, hagiology, hardheadedness,
   hierology, historical materialism, hylomorphism, hylotheism,
   hylozoism, infidelity, lack of feelings, logos Christology,
   logos theology, materialism, matter-of-factness, mechanism,
   minimifidianism, natural realism, natural theology, naturalism,
   neoorthodox theology, neoorthodoxy, new realism, nullifidianism,
   patristic theology, phenomenological theology, physicalism,
   physicism, physicotheology, positive philosophy, positivism,
   practical-mindedness, practicality, practicalness, pragmaticism,
   pragmatism, rationalism, rationality, realism, reasonableness,
   religion, representative realism, saneness, scholastic theology,
   scientism, sensibleness, sober-mindedness, soteriology,
   substantialism, systematics, temporality, theology, unbelief,
   unidealism, unromanticalness, unsentimentality, worldliness