plumb >> /pləm/
Definition: [noun] A plumb bob.
Example: He traces a line in white paint along the wall beyond the leaves, then drops a plumb from a cord stretched between two metal poles posted on either side of the tree.
Definition: [adjective] Vertical.
Example: ensure that the baseboard is straight and plumb
Definition: [transitive verb] Measure (the depth of a body of water)
Example: I plumbed the depth and found the bottom of the shelf to be seven meters down
Definition: [transitive verb] Test (an upright surface) to determine the vertical.
Example: they are valuable aids in plumbing the frames and keeping the side of the ship fair
Definition: [adverb] Exactly.
Definition: [adverb] Vertically.
Example: drapery fell from their human forms plumb down