Source : Webster's Revised Unabridged Dictionary (1913)

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}.]
   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.

   2. The essence; the best part.

            It takes from our achievements . . . The pith and
            marrow of our attribute.              --Shak.

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

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

   {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}.

Source : WordNet®

marrow squash
     n : any of various squash plants grown for their elongated fruit
         with smooth dark green skin and whitish flesh [syn: {marrow},
          {vegetable marrow}]