Bottom  —n. 1 a lowest point or part. B base. C underneath part. D furthest or inmost part. 2 colloq. A buttocks. B seat of a chair etc. 3 a less honourable end of a table, class, etc. B person occupying this (he's bottom of the class). 4 ground below water. 5 basis or origin. 6 essential character. —adj. Lowest, last. —v. 1 put a bottom to (a chair etc.). 2 find the extent of. 3 touch the bottom or lowest point (of).  at bottom basically. Be at the bottom of have caused. Bottom out reach the lowest level. Get to the bottom of fully investigate and explain. [old english]