LEARNit Dictionary
plumb line
noun
/ˈplʌm laɪn/
UK
/ˈplʌm laɪn/
US
1
a piece of thick string with a weight attached to one end, used to find the depth of water or to test whether a wall, etc. is straight
شاقول, خط شاقول, ریسمان سربی, نخ وزندار