marrow

(noun) the fatty network of connective tissue that fills the cavities of bones. Synonyms: bone marrow.

(noun) any of various squash plants grown for their elongated fruit with smooth dark green skin and whitish flesh. Synonyms: marrow squash, vegetable marrow.

(noun) very tender and very nutritious tissue from marrowbones. Synonyms: bone marrow.

(noun) large elongated squash with creamy to deep green skins. Synonyms: vegetable marrow.

(noun) the choicest or most essential or most vital part of some idea or experience. Synonyms: kernel, substance, core, center, centre, essence, gist, heart, heart and soul, inwardness, meat, nub, pith, sum, nitty-gritty. Examples: "The gist of the prosecutor's argument." "The heart and soul of the republican party." "The nub of the story."