SAT GRE plumb Definition Straight down or vertical; also, to measure the depth of something. Example "The arrow fell plumb to the ground." Sign in to save SAT PDF — $25 GRE PDF — $25 ← plumage plumber → Study tips featuring "plumb" How Context Clues Save You on the SAT Related words SAT antonym SAT abase SAT abdicate SAT abdomen SAT abduction SAT abet SAT abeyance SAT abject SAT abjure SAT ablution SAT abnegate SAT abnormal