The Collaborative International Dictionary of English v.0.48:

Secular \Sec"u*lar\, a. [OE. secular, seculer. L. saecularis,
   fr. saeculum a race, generation, age, the times, the world;
   perhaps akin to E. soul: cf. F. s['e]culier.]
   1. Coming or observed once in an age or a century.
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            The secular year was kept but once a century.
                                                  --Addison.
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   2. Pertaining to an age, or the progress of ages, or to a
      long period of time; accomplished in a long progress of
      time; as, secular inequality; the secular refrigeration of
      the globe.
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   3. Of or pertaining to this present world, or to things not
      spiritual or holy; relating to temporal as distinguished
      from eternal interests; not immediately or primarily
      respecting the soul, but the body; worldly.
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            New foes arise,
            Threatening to bind our souls with secular chains.
                                                  --Milton.
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   4. (Eccl.) Not regular; not bound by monastic vows or rules;
      not confined to a monastery, or subject to the rules of a
      religious community; as, a secular priest.
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            He tried to enforce a stricter discipline and
            greater regard for morals, both in the religious
            orders and the secular clergy.        --Prescott.
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   5. Belonging to the laity; lay; not clerical.
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            I speak of folk in secular estate.    --Chaucer.
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   Secular equation (Astron.), the algebraic or numerical
      expression of the magnitude of the inequalities in a
      planet's motion that remain after the inequalities of a
      short period have been allowed for.

   Secular games (Rom. Antiq.), games celebrated, at long but
      irregular intervals, for three days and nights, with
      sacrifices, theatrical shows, combats, sports, and the
      like.

   Secular music, any music or songs not adapted to sacred
      uses.

   Secular hymn or Secular poem, a hymn or poem composed for
      the secular games, or sung or rehearsed at those games.
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The Collaborative International Dictionary of English v.0.48:

Secular \Sec"u*lar\, n.
   1. (Eccl.) A secular ecclesiastic, or one not bound by
      monastic rules. --Burke.
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   2. (Eccl.) A church official whose functions are confined to
      the vocal department of the choir. --Busby.
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   3. A layman, as distinguished from a clergyman.
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WordNet (r) 3.0 (2006):

secular
    adj 1: of or relating to the doctrine that rejects religion and
           religious considerations
    2: characteristic of or devoted to the temporal world as opposed
       to the spiritual world; "worldly goods and advancement";
       "temporal possessions of the church" [syn: worldly,
       secular, temporal] [ant: unworldly]
    3: not concerned with or devoted to religion; "sacred and
       profane music"; "secular drama"; "secular architecture",
       "children being brought up in an entirely profane
       environment" [syn: profane, secular] [ant: sacred]
    4: of or relating to clergy not bound by monastic vows; "the
       secular clergy" [ant: religious]
    5: characteristic of those who are not members of the clergy;
       "set his collar in laic rather than clerical position"; "the
       lay ministry" [syn: laic, lay, secular]
    n 1: someone who is not a clergyman or a professional person
         [syn: layman, layperson, secular] [ant: clergyman,
         man of the cloth, reverend]

Moby Thesaurus II by Grady Ward, 1.0:

117 Moby Thesaurus words for "secular":
   Philistine, annual, biannual, biennial, bimonthly, biweekly,
   bodily, brother, carnal, carnal-minded, catamenial, catechumen,
   centenary, centennial, centesimal, centigrado, centuple,
   centuplicate, centurial, church member, churchman, churchwoman,
   civil, communicant, congregational, corporal, corporeal, daily,
   decennial, diurnal, down-to-earth, earthly, earthy, fleshly,
   fortnightly, hardheaded, hebdomadal, hourly, hundredfold,
   hundredth, hylic, laic, laical, lay, lay brother, lay sister,
   layman, laywoman, material, materialistic, materiate,
   matter-of-fact, menstrual, momentary, momently, monthly, mundane,
   nonclerical, nonecclesiastical, nonministerial, nonordained,
   nonpastoral, nonreligious, nonsacred, nonspiritual, parishioner,
   physical, popular, positivistic, practical, practical-minded,
   pragmatic, profane, quarterly, quotidian, rational, realist,
   realistic, reasonable, reprobate, sane, scientific, scientistic,
   secularist, secularistic, semestral, semiannual, semimonthly,
   semiweekly, semiyearly, sensible, sister, sober-minded, somatic,
   sound, sound-thinking, state, straight-thinking, substantial,
   temporal, terrestrial, tertian, triennial, unblessed, unhallowed,
   unholy, unideal, unidealistic, unregenerate, unromantic, unsacred,
   unsanctified, unsentimental, unspiritual, weekly, worldly,
   yearly