Webster's Revised Unabridged Dictionary · 1913

Plummet

Plummet , noun

[Old English plommet, Old French plommet, from plom, plum, lead, French plomb. See Plumb.]

1.
A piece of lead attached to a line, used in sounding the depth of water.
I'll sink him deeper than e'er plummet sounded. — Shakespeare
2.
A plumb bob or a plumb line. See under Plumb, n.
3.
Hence, any weight.
4.
A piece of lead formerly used by school children to rule paper for writing.
Collocations (1)
Plummet line , a line with a plummet; a sounding line.