plumb line

American  

noun

1. a cord with a lead bob attached to one end, used to determine perpendicularity, the depth of water, etc.

2. plumb rule.

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plumb line British  

noun

1. a string with a metal weight at one end that, when suspended, points directly towards the earth's centre of gravity and so is used to determine verticality, the depth of water, etc

2. another name for plumb rule

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plumb line Scientific  

/ plŭm /

1. A line regarded as directed exactly toward the Earth's center of gravity.

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Etymology

Origin of plumb line

First recorded in 1530–40

Example Sentences

Its southern latitude disguises just how far west the shipping channel reaches — far enough to catch a plumb line dropped from Cleveland.

From New York Times • May 18, 2018

He rolled up his sleeves, wiped the blade against the sole of his shoe, then hunkered down and closed one eye, like a carpenter with a plumb line.

From The New Yorker • Nov. 19, 2012

I had a beautiful Vidal-style pageboy, plumb line straight.

From BBC • May 24, 2012

As Mr. Bell and Mr. Cook flowed, their bats descending as if on a plumb line, Mr. Collingwood's lack of footwork and jerky movements, born of an increasingly inconspicuous back-lift are more apparent.

From The Wall Street Journal • Jan. 5, 2011

If a factory was nearby, he’d explain how you used a plumb line to get the chimney straight and why the windows had been placed a certain way to let in the maximum light.

From "Cheaper by the Dozen" by Frank B. Gilbreth Jr. and Ernestine Gilbreth Carey