To Plumb

1. To determine the depth, generally of a liquid; to sound.
2. To attach to a water supply and drain.
3. (transitive, figuratively) 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. (dated) To seal something with lead.
7. (intransitive) To work as a plumber.
8. (rare) To fall or sink like a plummet.
9. (US, colloquial, figuratively, obsolete) To trace a road or track; to follow it to its end.
10. (nautical) To position vertically above or below.