ˈstrōbəˌskōp, -räb- noun
Etymology: Greek strobos action of whirling + International Scientific Vocabulary -scope
: an instrument that is used for observing motion in such a way that moving objects (as machine parts) appear to be slowed down or stationary, that is used especially for determining speeds of rotation or frequencies of vibration, and that is made in the form of a revolving disk with holes around the edge through which an object is viewed or a rapidly flashing light that illuminates an object intermittently or a cardboard disk with marks to be viewed under intermittent light