The Collaborative International Dictionary of English v.0.48:

Buxom \Bux"om\, a. [OE. buxum, boxom, buhsum, pliable, obedient,
   AS. b[=o]csum, b[=u]hsum (akin to D. buigzaam blexible, G.
   biegsam); b[=u]gan to bow, bend + -sum, E. -some. See Bow
   to bend, and -some.]
   1. Yielding; pliable or compliant; ready to obey; obedient;
      tractable; docile; meek; humble. [Obs.]
      [1913 Webster]

            So wild a beast, so tame ytaught to be,
            And buxom to his bands, is joy to see. --Spenser.
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            I submit myself unto this holy church of Christ, to
            be ever buxom and obedient to the ordinance of it.
                                                  --Foxe.
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   2. Having the characteristics of health, vigor, and
      comeliness, combined with a gay, lively manner; stout and
      rosy; jolly; frolicsome.
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            A daughter fair,
            So buxom, blithe, and debonair.       --Milton.
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            A parcel of buxom bonny dames, that were laughing,
            singing, dancing, and as merry as the day was long.
                                                  --Tatler.
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   3. having a pronounced womanly shape. [chiefly dialect]

   Syn: bosomy, curvaceous, full-bosomed, sonsie, sonsy,
        voluptuous.
        [WordNet 1.5 +PJC] -- Bux"om*ly, adv. --
        Bux"om*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

buxomness
    n 1: the bodily property of being attractively plump and
         vigorous and (of women) full-bosomed