plumbto test the depth or examine the nature of something; to inquire into deeply (not just a bathroom fixture)The documentary plumbs the depths of human resilience in the face of natural disaster.NoteThe documentary plumbs the depths of human resilience in the face of natural disaster.Elon.io is an online learning platformWe have an entire course teaching GRE Verbal — Essential Vocabulary grammar and vocabulary.Start learning GRE Verbal — Essential Vocabulary now