The Collaborative International Dictionary of English v.0.48:

Beginning \Be*gin"ning\, n.
   1. The act of doing that which begins anything; commencement
      of an action, state, or space of time; entrance into being
      or upon a course; the first act, effort, or state of a
      succession of acts or states.
      [1913 Webster]

            In the beginning God created the heaven and the
            earth.                                --Gen. i. 1.
      [1913 Webster]

   2. That which begins or originates something; the first
      cause; origin; source.
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            I am . . . the beginning and the ending. --Rev. i.
                                                  8.
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   3. That which is begun; a rudiment or element.
      [1913 Webster]

            Mighty things from small beginnings grow. --Dryden.
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   4. Enterprise. "To hinder our beginnings." --Shak.
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   Syn: Inception; prelude; opening; threshold; origin; outset;
        foundation.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Begin \Be*gin"\, v. i. [imp. & p. p. Began, Begun; p. pr. &
   vb. n. Beginning.] [AS. beginnan (akin to OS. biginnan, D.
   & G. beginnen, OHG. biginnan, Goth., du-ginnan, Sw. begynna,
   Dan. begynde); pref. be- + an assumed ginnan. [root]31. See
   Gin to begin.]
   1. To have or commence an independent or first existence; to
      take rise; to commence.
      [1913 Webster]

            Vast chain of being! which from God began. --Pope.
      [1913 Webster]

   2. To do the first act or the first part of an action; to
      enter upon or commence something new, as a new form or
      state of being, or course of action; to take the first
      step; to start. "Tears began to flow." --Dryden.
      [1913 Webster]

            When I begin, I will also make an end. --1 Sam. iii.
                                                  12.
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WordNet (r) 3.0 (2006):

beginning
    adj 1: serving to begin; "the beginning canto of the poem"; "the
           first verse" [syn: beginning(a), first]
    n 1: the event consisting of the start of something; "the
         beginning of the war" [ant: conclusion, ending,
         finish]
    2: the time at which something is supposed to begin; "they got
       an early start"; "she knew from the get-go that he was the
       man for her" [syn: beginning, commencement, first,
       outset, get-go, start, kickoff, starting time,
       showtime, offset] [ant: end, ending, middle]
    3: the first part or section of something; "`It was a dark and
       stormy night' is a hackneyed beginning for a story" [ant:
       end, middle]
    4: the place where something begins, where it springs into
       being; "the Italian beginning of the Renaissance"; "Jupiter
       was the origin of the radiation"; "Pittsburgh is the source
       of the Ohio River"; "communism's Russian root" [syn:
       beginning, origin, root, rootage, source]
    5: the act of starting something; "he was responsible for the
       beginning of negotiations" [syn: beginning, start,
       commencement] [ant: finish, finishing]

Moby Thesaurus II by Grady Ward, 1.0:

130 Moby Thesaurus words for "beginning":
   abecedarian, aboriginal, alpha, anlage, antenatal, anticipation,
   appearance, authorship, autochthonous, babyhood, basal, beginnings,
   birth, budding, childhood, coinage, commencement, conception,
   concoction, contrivance, contriving, cradle, creation, creative,
   creative effort, dawn, dawning, day, derivation, devising,
   earliness, early hour, early stage, elemental, elementary,
   embryonic, emergence, fabrication, fetal, first crack, first stage,
   foresight, formative, foundational, freshman year, fundamental,
   generation, genesis, gestatory, grass roots, ground floor,
   hatching, head, head start, improvisation, in embryo,
   in its infancy, in the bud, inaugural, inception, inceptive,
   inchoate, inchoation, inchoative, incipience, incipiency,
   incipient, incunabula, incunabular, infancy, infant, infantile,
   initial, initiative, initiatory, introductory, invention,
   inventive, making do, mintage, nascence, nascency, nascent, natal,
   nativity, onset, opening, origin, original, origination, outset,
   outstart, parturient, parturition, postnatal, pregnancy, pregnant,
   prenatal, prevenience, prevision, primal, primary, prime, primeval,
   primitive, primogenial, procreative, prologue, provenience,
   radical, radix, readiness, rise, root, rudiment, rudimental,
   rudimentary, running start, setout, source, spring, sprout, start,
   stem, stock, taproot, time to spare, ur, very beginning, youth