PLUMMET

[plum.met] n [ME plomet, fr. MF plombet ball of lead, fr. plomb lead, fr. (assumed) OF--more at plumb] (14c): plumb; also: plumb line

[2]plummet vi (1937) 1: to fall perpendicularly "birds ~ed down"

2: to drop sharply and abruptly "prices ~ed"