Plummet meaning : A piece of lead attached to a line, used in sounding the depth of water, a plumb bob or a plumb line Hence, any weight A piece of lead formerly used by school children to rule paper for writing (that is, to mark with rules, with lines) A plummet line, a line with a plummet; a sounding line Violent or dramatic fall A decline; a fall; a drop To drop swiftly, in a direct manner; to fall quickly.