What does "plumb" mean?

Plumb: To adjust by a plumb line; to cause to be perpendicular; as, to plumb a building or a wall.

Additional senses

  1. 2.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. He did not attempt to plumb his intellect. Ld. Lytton.
  2. 3.To seal with lead; as, to plumb a drainpipe.
  3. 4.To supply, as a building, with a system of plumbing.

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