adv in a plumb direction; perpendicularly.
2. plumb ·vt to seal with lead; as, to plumb a drainpipe.
3. plumb ·vt to supply, as a building, with a system of plumbing.
4. plumb ·vt to adjust by a plumb line; to cause to be perpendicular; as, to plumb a building or a wall.
5. plumb ·adj perpendicular; vertical; conforming the direction of a line attached to a plumb; as, the wall is plumb.
6. plumb ·noun 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.
7. plumb ·vt 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.