1. The angle that an emerging seismic wavefront makes with the surface; the angle whose tangent is the ratio of the vertical-to-horizontal components of displacement produced by a P-wavefront. Apparent dip can be related to the true dip of the reflector if the cross-dip and velocity distribution are known. Compare dip moveout and apparent velocity. 2. The angle from horizontal for a refracting horizon determined from the updip and downdip velocities of head waves; see Figure R-10. 3. The dip of a rock layer exposed in a section that is not at a right angle to the strike.