plumb

¹ American  

[pluhm] / plʌm /

noun

1. a small mass of lead or other heavy material, as that suspended by a line and used to measure the depth of water or to ascertain a vertical line.

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adjective

1. true according to a plumb line perpendicular.

   Synonyms:

   square, straight, vertical

2. Informal. downright or absolute.

adverb

1. in a perpendicular or vertical direction.

2. exactly, precisely, or directly.

3. Informal. completely or absolutely.

   She was plumb mad. You're plumb right.

verb (used with object)

1. to test or adjust by a plumb line.

2. to make vertical.

3. Shipbuilding. horn.

4. to sound with or as with a plumb line.

5. to measure (depth) by sounding.

6. to examine closely in order to discover or understand.

   to plumb someone's thoughts.

7. to seal with lead.

8. to weight with lead.

9. to provide (a house, building, apartment, etc.) with plumbing.

verb (used without object)

1. to work as a plumber.

idioms

1. out of / off plumb, not corresponding to the perpendicular; out of true.

Plumb ² American  

[pluhm] / plʌm /

noun

1. J(ohn) H(arold), 1911–2001, British historian.

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plumb British  

/ plʌm /

noun

1. a weight, usually of lead, suspended at the end of a line and used to determine water depth or verticality

2. the perpendicular position of a freely suspended plumb line (esp in the phrases out of plumb, off plumb )

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adjective

1. informal (prenominal) (intensifier)

   a plumb nuisance

adverb

1. in a vertical or perpendicular line

2. informal (intensifier)

   plumb stupid

3. informal exactly; precisely (also in the phrase plumb on )

verb

1. to test the alignment of or adjust to the vertical with a plumb line

2. (tr) to undergo or experience (the worst extremes of misery, sadness, etc)

   to plumb the depths of despair

3. (tr) to understand or master (something obscure)

   to plumb a mystery

4. to connect or join (a device such as a tap) to a water pipe or drainage system

Other Word Forms

• plumbable adjective
• plumbless adjective
• plumbness noun
• replumb verb (used with object)
• unplumb adjective

Etymology

Origin of plumb

1250–1300; Middle English plumbe, probably < Anglo-French *plombe < Vulgar Latin *plumba, for Latin plumbum lead

Example Sentences

The Depository Trust & Clearing Corp. has framed the initiative as an incremental modernization of post-trade plumbing rather than a wholesale rewrite of market structure, with an initial rollout targeted for the second half of 2026.

From MarketWatch

The ballot will be for about 1,000 members of staff who are part of Unite the Union, mainly involved in housing maintenance work, like plumbing and heating engineering.

From BBC

Her challenging books demand to be plumbed, debated, compared—and reread.

From The Wall Street Journal

And even if the residents are allowed to return, they wouldn’t be able to build new homes until the owners fix or replace damaged foundations and hookups for electricity and plumbing.

From Los Angeles Times

The bit remains frustratingly shallow, when there’s so much opportunity to plumb what it means to seek solace in smoothies and faux spirituality.

From Los Angeles Times

Related Words

• delve
• explore
• fathom
• penetrate
• unravel