plumb bob

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A usually conical metal weight attached to the end of a plumb line. Also called plummet.

Century Dictionary and Cyclopedia

1. n. A conoid-shaped metal bob or weight attached to the end of a plumb-line. See also cut under plumb-rule.

Wiktionary

1. n. A metal weight attached to the end of a plumb line.

GNU Webster's 1913

1. n. See Bob, 4.

WordNet 3.0

1. n. the metal bob of a plumb line