say it: pluhm
plumb is a verb, adverb, noun and adjective meaning "measure the depth of something". It carries 9 recorded senses.
conforming to the direction of a plumb line
the metal bob of a plumb line
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for plumb come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.