sounding- ¹ Measuring the depth of water with a lead line or by other means. ² Depth so measured; [pl. soundings] a place, usually less than 100 fathoms (c. 180 m) in depth, where a sounding line will touch bottom. ³ [ENGINEERING] Data acquired by pushing or driving a steel rod down through the soil as far as it will penetrate with the equipment at hand. As samples cannot be obtained by this method, no information relative to the physical properties or moisture content of the soil is obtained. Only a record of the resistance to penetration at various depths is derived. Changes in strata are noted only when there is a definite change in resistance to penetration as in passing from silt to gravel or from gravel to clay. Soundings are made by some engineers to estimate the approximate length of pile required in a given location. Soundings are most useful in soft materials to determine the depth of a solid stratum. Also referred to as “probing.” ⁴ An examination of the atmosphere at or to a given height, as with a radiosonde; a probe of space, as with a rocket. ⁵ [often pl.] An exploratory sampling, as of public opinion.

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Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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