plumb line
鉛垂線
Plumb n. A little mass or weight of lead, or the like, attached to a line, and used by builders, etc., to indicate a vertical direction; a plummet; a plumb bob. See Plumb line, below.
Plumb bob. See Bob, 4.
Plumb joint, in sheet-metal work, a lap joint, fastened by solder.
Plumb level. See under Level.
Plumb line. (a) The cord by which a plumb bob is suspended; a plummet. (b) A line directed to the center of gravity of the earth.
Plumb rule, a narrow board with a plumb line, used by builders and carpenters.
plumb line
n : a cord from which a metal weight is suspended pointing
directly to the earth's center of gravity; used to
determine the vertical from a given point [syn: perpendicular]