plumb

1 of 4

noun

ˈpləm 

: a lead weight attached to a line and used to indicate a vertical direction

plumb

2 of 4

adverb

1

: straight down or up : vertically

2

chiefly dialectal : to a complete degree : absolutely

'you're plumb crazy', she remarked, with easy candor

—Harper's Weekly

3

: in a direct manner : exactly

also : without interval of time : immediately

plumb

3 of 4

verb

plumbed; plumbing; plumbs

transitive verb

1

: to weight with lead

2

a

: to measure the depth of with a plumb

b

: to examine minutely and critically

plumbing the book's complexities

3

: to adjust or test by a plumb line

4

: to seal with lead

5

[back-formation from plumber] : to supply with or install as plumbing

intransitive verb

: to work as a plumber

plumb

4 of 4

adjective

1

: exactly vertical or true

2

: thorough, complete

Phrases

out of plumb or off plumb

: out of vertical or true

Synonyms

Adverb

• dead
• direct
• directly
• due
• plump
• right
• straight
• straightway

Verb

• fathom
• sound

Adjective

• absolute
• all-out
• arrant
• blank
• blooming [chiefly British]
• bodacious [Southern & Midland]
• categorical
• categoric
• clean
• complete
• consummate
• crashing
• damn
• damned
• dead
• deadly
• definite
• downright
• dreadful
• fair
• flat
• flat-out
• out-and-out
• outright
• perfect
• profound
• pure
• rank
• regular
• sheer
• simple
• stark
• stone
• straight-out
• thorough
• thoroughgoing
• total
• unadulterated
• unalloyed
• unconditional
• unmitigated
• unqualified
• utter
• very

Choose the Right Synonym for plumb

vertical, perpendicular, plumb mean being at right angles to a base line.

vertical suggests a line or direction rising straight upward toward a zenith.

the side of the cliff is almost vertical

perpendicular may stress the straightness of a line making a right angle with any other line, not necessarily a horizontal one.

the parallel bars are perpendicular to the support posts

plumb stresses an exact verticality determined (as with a plumb line) by earth's gravity.

make sure that the wall is plumb

Examples of plumb in a Sentence

Adverb

He set the board plumb.

I plumb forgot about the party.

Verb

The book plumbs the complexities of human relationships.

a scientist who spent her life plumbing the minds of criminals

The play plumbs the depths of human nature.

The plumber is almost finished plumbing the apartment.

The new house has been wired and plumbed.

All the bathroom fixtures have been plumbed.

Adjective

The carpenter made sure that the wall was plumb.

a horror movie that's plumb trash and further evidence of the deterioration of popular culture

Recent Examples on the Web

Noun

In 1990, when the angle passed five degrees, and the top of the tower was fifteen feet out of plumb, the structure was said to be finally in danger of collapsing. —Eric Lach, The New Yorker, 3 Feb. 2025

There’s a wealth of themes to plumb, from familial trauma to addiction to sexism to the tyranny of genius, but its core exploration of the sacrifice required to be an artist is exhilarating, brutal, and intoxicating. —Ew Staff, EW.com, 11 Dec. 2024

Verb

The German composer, whose work often plumbed the ancient past, came across them in 1934. —Tim Greiving, Los Angeles Times, 12 Mar. 2025

His boundless contempt for it plumbed a new low with an executive order demanding, among other things, that everyone must show proof of citizenship before being allowed to register or update their voting registrations. —Sun Sentinel Editorial Board, Sun Sentinel, 28 Mar. 2025

Adjective

Mars will appear plumb against its sparkling stars tonight — though the couple of nights either side will also give a great binocular view. —Jamie Carter, Forbes, 6 Mar. 2025

Its clean lines with plumb bow at first appear European, though the twin outboards at the stern signify it as an American boat. —Michael Verdon, Robb Report, 14 Feb. 2025

Word History

Etymology

Noun

Middle English, from Anglo-French plum, plomb, from Latin plumbum lead

First Known Use

Noun

14th century, in the meaning defined above

Adverb

15th century, in the meaning defined at sense 1

Verb

15th century, in the meaning defined at transitive sense 1

Adjective

15th century, in the meaning defined at sense 1

Phrases Containing plumb

• plumb bob
• plumb in
• plumb line
• plumb new depths
• plumb the depths of

Rhymes for plumb

• bum
• chum
• come
• crum
• cum
• drum
• dum
• dumb
• from
• frum
• glum
• gum

Kids Definition

plumb

1 of 4 noun

ˈpləm 

: a weight attached to a line especially to show a vertical direction or distance

plumb

2 of 4 adverb

1

: straight down or up : vertically

2

chiefly dialect : to a complete degree : absolutely

3

: in a direct manner : exactly

plumb

3 of 4 verb

1

: to measure, adjust, or test with a plumb

plumb a wall

plumb the depth of the well

2

: to see into and come to understand

plumbed their motives

plumb

4 of 4 adjective

: exactly vertical or true

the wall is plumb