plummet

noun

1. (archaic)A piece of lead attached to a line, used in sounding the depth of water; a plumb bob or a plumb line.

   “I'le ſeeke him deeper than ere plummet ſounded, / And with him there lye mudded.”

   “Iudgement also will I lay to the line, and righteousnesse to the plummet: and the haile shall sweepe away the refuge of lyes, and the waters shall ouerflow the hiding place.”

   “Each long black hair upon his head hung down as straight as any plummet line; […]”

   “And love was the plummet dropped down into the deeps of him where like had never gone.”

   “He told her then of his life since he had returned to the jungle—of how he had dropped like a plummet from a civilized Parisian to a savage Waziri warrior, and from there back to the brute that he had been raised.”

2. (archaic)Hence, any weight.

   “His parachute was shot half away, and if he'd jumped he would have fallen like a plummet.”

3. (archaic)A piece of lead formerly used by schoolchildren to rule paper for writing (that is, to mark with rules, with lines).
4. A violent or dramatic fall.
5. (figuratively)A decline; a fall; a drop.

   “Yet another seriously under-par performance is unlikely to provide any real answers to their remarkable plummet in form - but it proves they can at least churn out a much-needed result.”

verb

1. (idiomatic, intransitive)To drop swiftly, in a direct manner; to fall quickly.

   “After its ascent, the arrow plummeted to earth.”

   “The switchback road to Diabaig - pronounced 'Jer-vague' - passes through some of the most exhilarating scenery in Scotland. […] With a final swoop, the road plummets down into Diabaig, where cottages are dotted across the slopes of a rocky semi-circle.”

   “Some speculated Twitter’s stock would plummet, while another said the company would not have to be owned by “a moron,” using an expletive to refer to Mr. Musk.”

   “Passenger numbers had been rising sharply. But the replacement of the services by buses, which take far longer because of the number of stations in out-of-the-way villages on the route, will ensure they plummet again.”