PLUMB

I. noun Etymology: Middle English, from Anglo-French plum, plomb, from Latin ~um lead Date: 14th century a lead weight attached to a line and used to indicate a vertical direction, II. adverb Date: 15th century straight down or up ; vertically, to a complete degree ; absolutely , in a direct manner ; exactly , III. verb Date: 15th century transitive verb to weight with lead, 2. to measure the depth of with a ~, to examine minutely and critically , to adjust or test by a ~ line, to seal with lead, to supply with or install as ~ing, intransitive verb to work as a ~er, IV. adjective Date: 15th century exactly vertical or true, thorough , complete , see: vertical