Definition of plumb

• n. - A little mass or weight of lead, or the like, attached to a line, and used by builders, etc., to indicate a vertical direction; a plummet; a plumb bob. See Plumb line, below.
• a. - Perpendicular; vertical; conforming the direction of a line attached to a plumb; as, the wall is plumb.
• adv. - In a plumb direction; perpendicularly.
• v. t. - To adjust by a plumb line; to cause to be perpendicular; as, to plumb a building or a wall.
• v. t. - To sound with a plumb or plummet, as the depth of water; hence, to examine by test; to ascertain the depth, quality, dimension, etc.; to sound; to fathom; to test.
• v. t. - To seal with lead; as, to plumb a drainpipe.
• v. t. - To supply, as a building, with a system of plumbing.