Synonyms for Plumb (same or very similar meaning)
WordNet sense 1 (the metal bob of a plumb line):
plummet, plumb bobWordNet sense 2 (at right angles to the plane of the horizon or a base line):
perpendicular, verticalWordNet sense 3 (exactly):
plumWordNet sense 4 (completely; used as intensifiers):
cleanFrom the ODE community, based on WordNetadd/edit