plum·met 
(plŭmĭt)
(plŭmĭt)n.
1. See plumb bob.
2. Something that weighs down or oppresses; a burden.
intr.v. plum·met·ed, plum·met·ing, plum·mets
1. To fall straight down; plunge.
2. To decline suddenly and steeply: Stock prices plummeted.
[Middle English plomet, from Old French, ball of lead, diminutive of plom, plomb, sounding lead, from Latin plumbum.]