plumb bob
- noun
- /plʌm bɑb/
:
plomada
- The new Astronomer Royal, Nevil Maskelyne, had become interested in the question of the effect of local gravity on a plumb bob, and Mason, no stranger to exploration, was sent to Scotland to find a suitable mountain where they could run an experiment.
- a plumb bob hanging
Examples
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The builder carefully lowered the plumb bob to ensure the wall was perfectly vertical.
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Because one cannot see a true horizon in the woods, the sector looked at the zenith; it was essentially a telescope mounted vertically and adjusted with an internal plumb bob.
Academic text (2006) -
Not only looks like, it is a plumb bob.
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"Have you ever heard of a level or a plumb-bob?" I asked when I still lived there.
Fiction book (2001) -
At each end of the cross, a plumb bob was hung.
Academic text (2003) -
It looks like a top, a surveyor's instrument, a plumb bob.
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Alec, the plumb bob.
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To check the alignment of the poles, we used a plumb bob hanging from a string.
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He attached a heavy plumb bob to the line, securing its position to mark the vertical reference.
Synonyms
8
7.4
A small heavy weight on a string used to find a perfectly vertical line
2
7.5
A small heavy metal weight used to check vertical lines
Surface Forms
Morphology
The meaning is directly compositional: 'plumb' relates to vertical alignment and 'bob' is a heavy weight suspended on a line, so together they denote a weight used to establish verticality. This straightforward noun-noun compound follows transparent word-formation patterns and a B1 learner who knows both constituents would readily infer the MWE's meaning.
Etymology
Plumb bob is a heavy, pointed weight called the bob that hangs from a string to show a plumb, which is a perfectly 'straight up-and-down' line. That's why builders use a plumb bob to mark a true straight line when they need something perfectly vertical.