1. (noun)substance the real physical matter of which a person or thing consists
"DNA is the substance of our genes"
2. (noun)kernel, substance, core, center, centre, essence, gist, heart, heart and soul, inwardness, marrow, meat, nub, pith, sum, nitty-gritty 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"
3. (noun)meaning, substance the idea that is intended
"What is the meaning of this proverb?"