plummets >> /ˈplʌmɪt/
Definition: [verb] Fall or drop straight down at high speed.
Example: a climber was killed when he plummeted 300 feet down an icy gully
Definition: [noun] A steep and rapid fall or drop.
Example: the bird has a circular display flight followed by an earthward plummet
Definition: [noun] A plumb or plumb line.
Example: With a heavy plummet, I plumb the depth and set the float so that about half the float's length is protruding above the surface.