nub (

     n 1: a small lump or protuberance
     2: a small piece; "a nub of coal" or "a stub of a pencil" [syn:
     3: 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, essence, gist, heart, heart and soul, inwardness,
         marrow, meat, pith, sum, nitty-gritty]