in a perpendicular or vertical direction.
exactly, precisely, or directly.
Informal. completely or absolutely.
She was plumb mad. You're plumb right.
to test or adjust by a plumb line.
to make vertical.
Shipbuilding. horn.
to sound with or as with a plumb line.
to measure (depth) by sounding.
to examine closely in order to discover or understand.
to plumb someone's thoughts.
to seal with lead.
to weight with lead.
to provide (a house, building, apartment, etc.) with plumbing.
a weight, usually of lead, suspended at the end of a line and used to determine water depth or verticality
the perpendicular position of a freely suspended plumb line (esp in the phrases out of plumb, off plumb )
in a vertical or perpendicular line
informal (intensifier)
plumb stupid
informal exactly; precisely (also in the phrase plumb on )
to test the alignment of or adjust to the vertical with a plumb line
(tr) to undergo or experience (the worst extremes of misery, sadness, etc)
to plumb the depths of despair
(tr) to understand or master (something obscure)
to plumb a mystery
to connect or join (a device such as a tap) to a water pipe or drainage system
1250–1300; Middle English plumbe, probably < Anglo-French *plombe < Vulgar Latin *plumba, for Latin plumbum lead
To plumb a body of water, you measure its depth. To plumb a house, you connect all of its pipes. To make carpentry plumb, you get it exactly vertical. Originally, the verb plumb only meant “to measure the depth of water.” These days, if you “plumb the depths” of something, you go in deep for knowledge and experience: your Heidegger seminar may plumb the depths of German Existentialism like Jacques Cousteau plumbed the depths of the ocean.
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Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Plumb said he has made all the budget cuts needed so far.
From The Wall Street Journal • Apr. 9, 2026
Plumb and his faculty leaders weighed the cost to run courses against the enrollment and value for students.
From The Wall Street Journal • Apr. 9, 2026
Meanwhile, Jack Plumb, 38, also from Suffolk, said the group and the yoga has helped battle his loneliness.
From BBC • Apr. 3, 2026
Sasha Wass KC, for Plumb, argued there was "no suggestion of lasting psychological harm" suffered by the victim, who has also presented I'm A Celebrity, Get Me Out Of Here.
From BBC • Oct. 21, 2025
Under the Plumb plan the government is to purchase the roads from their present owners, paying with government bonds.
From The Book of Life by Sinclair, Upton
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
