plumb bob

plumb bob — noun

1. a small heavy weight hung from a cord, used to check whether a wall, post, or su

1.nounC2
Definition

a small heavy weight hung from a cord, used to check whether a wall, post, or surface is exactly vertical

Example

The carpenter hung a plumb bob beside the frame before fixing it in place.

hung a plumb bob to check alignment

A simple plumb bob showed that the garden post was leaning slightly.

showed that the post was not vertical

Common collocations
  • hang a plumb bob
  • use a plumb bob
  • plumb bob and string
  • check with a plumb bob
Synonyms
  • plummet

    older or technical word for the same kind of hanging weight

  • plumb line

    the line and weight together, or sometimes the whole tool

Grammar Patterns

a plumb bob

hang a plumb bob

use a plumb bob to check + noun

Usage Note

A plumb bob is the weight at the end of a plumb line. The whole tool may also be called a plumb line in everyday use.

Common Mistakes

Do not write 'plum bob' in technical writing; the building tool is spelled 'plumb bob'.

Word family

  • plumb
    adjectiveC2
  • plumb line
    nounC2
  • plummet
    nounC2

Synonym discussion

Sense: noun/1

A plumb bob is the hanging weight itself. A plumb line is the cord with the weight attached, and in ordinary speech it can mean the whole tool. Plummet is an older or more technical name for the weight. A level checks whether something is horizontal or flat, while a plumb bob checks vertical alignment.

plumb bob ↗plumb lineplummet ↗level ↗

Common collocations

Nouns

Verbs

Phrases

  • hang a plumb bob
  • use a plumb bob
  • check with a plumb bob
  • plumb bob and string

Etymology

LatinOld FrenchEnglish

Plumb comes from a Latin word for lead, because early weights for checking vertical lines were often made of lead. Bob here means a small hanging weight.

First known use

1836

1836, in the meaning defined above