1. (n.) A weight attached to a line and used by builders to indicate a vertical direction; a plummet; a plumb bob. See below.

2. (a.) Perpendicular; vertical; conforming the direction of a line attached to a plumb; as, the wall is plumb.

3. (adv.) In a plumb direction; perpendicularly.

4. (v. t.) To adjust by a plumb line; to cause to be perpendicular; as, to plumb a building or a wall.

5. (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.

6. (v. t.) To seal with lead; as, to plumb a drainpipe.

7. (v. t.) To supply, as a building, with a system of plumbing.