plumb

/plʌm/

noun

1
A little mass of lead, or the like, attached to a line, and used by builders, etc., to indicate a vertical direction.
2
A weight on the end of a long line, used by sailors to determine the depth of water.
3
The perpendicular direction or position.

1
To determine the depth, generally of a liquid; to sound.
2
To attach to a water supply and drain.
3
To think about or explore in depth, to get to the bottom of, especially to plumb the depths of.
4
To use a plumb bob as a measuring or aligning tool.
5
To accurately align vertically or horizontally.
6
To seal something with lead.
7
To work as a plumber.
8
To fall or sink like a plummet.
9
To trace a road or track; to follow it to its end.
10
To position vertically above or below.

1
Truly vertical, as indicated by a plumb line.
2
Describing an LBW where the batsman is hit on the pads directly in front of his wicket and should be given out.