DIP, in magnetism (see TERRESTRIAL MAGNETISM), the angle made by the direction of the earth's magnetic field and the hori zontal is the angle of dip, commonly called the dip. In astronomy (q.v.) and surveying (q.v.) the dip of the horizon is the angular distance between the true horizon and the apparent horizon, due to the observer's elevation. In geology (q.v.) the angle which the line of maximum slope of a stratum makes with the horizontal.