The Collaborative International Dictionary of English v.0.48:

Marrow \Mar"row\, v. t. [imp. & p. p. Marrowed; p. pr. & vb.
   n. Marrowing.]
   To fill with, or as with, marrow or fat; to glut.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Marrow \Mar"row\, n. [OE. marou, mary, maruh, AS. mearg, mearh;
   akin to OS. marg, D. merg, G. Mark, OHG. marg, marag, Icel.
   mergr, Sw. merg, Dan. marv, Skr. majjan; cf. Skr. majj to
   sink, L. mergere. [root]274 Cf. Merge.]
   [1913 Webster]
   1. (Anat.) The tissue which fills the cavities of most bones;
      the medulla. In the larger cavities it is commonly very
      fatty, but in the smaller cavities it is much less fatty,
      and red or reddish in color.
      [1913 Webster]

   2. The essence; the best part.
      [1913 Webster]

            It takes from our achievements . . .
            The pith and marrow of our attribute. --Shak.
      [1913 Webster]

   3. [OE. maru, maro; -- perh. a different word; cf. Gael.
      maraon together.] One of a pair; a match; a companion; an
      intimate associate. [Scot.]
      [1913 Webster]

            Chopping and changing I can not commend,
            With thief or his marrow, for fear of ill end.
                                                  --Tusser.
      [1913 Webster]

   Marrow squash (Bot.), a name given to several varieties of
      squash, esp. to the Boston marrow, an ovoid fruit,
      pointed at both ends, and with reddish yellow flesh, and
      to the vegetable marrow, a variety of an ovoid form, and
      having a soft texture and fine grain resembling marrow.

   Spinal marrow. (Anat.) See Spinal cord, under Spinal.
      [1913 Webster]

WordNet (r) 3.0 (2006):

marrow
    n 1: the fatty network of connective tissue that fills the
         cavities of bones [syn: marrow, bone marrow]
    2: any of various squash plants grown for their elongated fruit
       with smooth dark green skin and whitish flesh [syn: marrow,
       marrow squash, vegetable marrow]
    3: very tender and very nutritious tissue from marrowbones [syn:
       marrow, bone marrow]
    4: large elongated squash with creamy to deep green skins [syn:
       marrow, vegetable marrow]
    5: the choicest or most essential or most vital part of some
       idea or experience; "the gist of the prosecutor's argument";
       "the heart and soul of the Republican Party"; "the nub of the
       story" [syn: kernel, substance, core, center,
       centre, essence, gist, heart, heart and soul,
       inwardness, marrow, meat, nub, pith, sum, nitty-
       gritty]