Synonyms for Plummet:

n.

decrease, shrink, diminish, dwindle. fall (noun)
nose dive.
plummet (noun)
plumb, plumb bob, plump.
plunge (noun)
nosedive.

v.

descend (verb)
fall, settle, slump, slip, decline, go down, drop, plunge, descend, sink, fall down, pitch, tumble, topple, come down, lower, slide.
dive (verb)
plumb.
drop (verb)
lower, plump.
fall (verb)
diminish, dwindle.
motion (verb)
plump.
plummet (verb)
descend, sink, tumble, dive, decline, skid, swoop, plunge, drop, decrease, fall.
plunge (verb)
dive, pitch, swoop.

Other synonyms:

nose dive, skid. go down.

Usage examples for plummet

  1. In the conversation which followed, old Jombatiste, exploring at last Cousin Tryphena's mind, leaned giddily over the abyss of her ignorance of political economy and sociology, dropping one exploring plummet after another into its depths, only to find them fathomless. – Hillsboro People by Dorothy Canfield
  2. Whirling the heavy plummet round his head, he let it shoot forward to the break of the forecastle, and steadied the line a moment when it ran vertically up and down. – The Coast of Adventure by Harold Bindloss
  3. And thus patiently did Walsingham pick his course, plummet in hand, through the mists and along the quicksands, and faithfully did he hold out signals to his comrade embarked on the same dangerous voyage. – Project Gutenberg History of The Netherlands, 1555-1623, Complete by John Lothrop Motley