► 動詞突き詰める  [(4)つきつめる]    
meaning:  do thoroughly  rank: 3☆ 
彼は
何事も突き詰めないと
気が
済まない
質だ ⇨ He’s a kind of person who has to get to the very bottom of everything
突き詰める  [(4)つきつめる]    
meaning:  essence  rank: 3☆ 突き詰めて
言えば… ⇨ Ultimately speaking … At the very core of the matter …