a lead weight attached to a cord and used to determine the depth of water or to gauge the verticality of a surface, line, or edge

any of various weights, such as a sinker for a fishing line

informal exactly; precisely

His house is plumb in the middle of the island

chiefly NAmer, informal completely; absolutely

Have you gone plumb crazy?

archaic straight down or up; vertically

to measure (the depth of water) with a plumb

to examine (something) minutely and critically, esp in order to understand it

He was plumbing the book's complexities

to adjust or test (the trueness or verticality of a surface, line, or edge) by a plumb line

to experience or endure, or explore and describe (the most extreme form of something unpleasant or unwelcome)

He had plumbed the depths of human misery

exactly vertical or true

said of a cricket wicket: flat and allowing little or no horizontal or vertical deviation of the bowled ball