CLINOMETER

n. instrument that measures slopes

A clinometer also known as an inclinometer is an instrument for measuring angles of slope (or tilt), elevation or inclination of an object with respect to gravity. Also known as a tilt meter, tilt indicator, slope meter, slope gauge, gradient meter, gradiometer, level gauge, level meter, pitch & roll indicator.
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Noun
1. an instrument used by surveyors in order to measure an angle of inclination or elevation
(synonym) inclinometer
(hypernym) surveying instrument, surveyor's instrument

n. instrument that measures slopes

(n.)
An instrument for determining the dip of beds or strata, pr the slope of an embankment or cutting; a kind of plumb level.