plumbline, plumb-line

Concise Bible Dictionary:

The simple contrivance of a lump of lead, a stone, or other weight attached to a string, for testing whether a building or other erection is perpendicular. It is used symbolically for the exactness with which judgment was brought upon Israel. Israel had been built up by God as a wall with a plumbline, and with a plumbline it should be destroyed (Amos 7:7-87Thus he showed me: and, behold, the Lord stood upon a wall made by a plumbline, with a plumbline in his hand. 8And the Lord said unto me, Amos, what seest thou? And I said, A plumbline. Then said the Lord, Behold, I will set a plumbline in the midst of my people Israel: I will not again pass by them any more: (Amos 7:7‑8); compare 2 Kings 21:1313And I will stretch over Jerusalem the line of Samaria, and the plummet of the house of Ahab: and I will wipe Jerusalem as a man wipeth a dish, wiping it, and turning it upside down. (2 Kings 21:13); Isa. 28:1717Judgment also will I lay to the line, and righteousness to the plummet: and the hail shall sweep away the refuge of lies, and the waters shall overflow the hiding place. (Isaiah 28:17)). In Zechariah 4:1010For who hath despised the day of small things? for they shall rejoice, and shall see the plummet in the hand of Zerubbabel with those seven; they are the eyes of the Lord, which run to and fro through the whole earth. (Zechariah 4:10), although it was a day of small things when the temple was rebuilt, the plummet was in the hands of Zerubbabel, and the Lord of hosts was supporting him.
Plumbline – Ivory – Roman and Greek Art

Strong’s Dictionary of Hebrew Words:

probably from an unused root meaning to be narrow; according to most a plumb-line, and to others a hook
KJV Usage: