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

Drop a plumb line from the top of the head down through the spine into the heels in first position, divide the body down this center, right from left.

From New York Times • Oct. 31, 2022

My father’s simple existence has been like a horizontal plumb line for me, one to gauge myself against.

From The Wall Street Journal • Jun. 14, 2018

He is depicted on his tomb with his tools - a set square and a plumb line.

From BBC • Dec. 25, 2013

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

The next day, they came back with a plumb line and a ruler to measure every distance between every component.

From "The Gene" by Siddhartha Mukherjee