nub[noun]Synonyms: substance, core, crux, gist, kernel, meat, nubbin, pith, short, upshot
 [TahlilGaran] English Synonym Dictionary ▲
 nub /nʌb/ 
 noun[
Date: 1500-1600; 
Origin: Probably from Low German knubbe]
1.  the nub of the problem/matter/argument etc the main point of a problem etc: 
 The real nub of the matter is money.2.  [countable] a small rounded piece of something, especially a piece that is left after the rest has been eaten, used etc 
 [TahlilGaran] Dictionary of Contemporary English ▲