'Sounding line' definitions:

Definition of 'sounding line'

noun

(nautical) plumb line for determining depth [syn: lead line, sounding line]

From: GCIDE

Sounding \Sound"ing\, n.
1. The act of one who, or that which, sounds (in any of the senses of the several verbs). [1913 Webster]
2. (Naut.) [From Sound to fathom.] (a) measurement by sounding; also, the depth so ascertained. (b) Any place or part of the ocean, or other water, where a sounding line will reach the bottom; -- usually in the plural. (c) The sand, shells, or the like, that are brought up by the sounding lead when it has touched bottom. [1913 Webster]
Sounding lead, the plummet at the end of a sounding line.
Sounding line, a line having a plummet at the end, used in making soundings.
Sounding post (Mus.), a small post in a violin, violoncello, or similar instrument, set under the bridge as a support, for propagating the sounds to the body of the instrument; -- called also sound post.
Sounding rod (Naut.), a rod used to ascertain the depth of water in a ship's hold.
In soundings, within the eighty-fathom line. --Ham. Nav. Encyc. [1913 Webster]