D defs.my
Entry 4 senses Webster, 1913

Plummet

/plŭm'-ət/ · Plum·met · IPA /ˈplʌmət/
01 n. A piece of lead attached to a line, used in sounding the depth of water.
  1. 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.” Shak.
  2. 2.
    A plumb bob or a plumb line. See under Plumb, n. See: Plumb
  3. 3.
    Hence, any weight.
  4. 4.
    A piece of lead formerly used by school children to rule paper for writing.
Phrases & compounds
Plummet line — a line with a plummet; a sounding line.