1. n. []

A subsurface boundary or interface at which a physical quantity, such as the velocity of transmission of seismic waves, changes abruptly. The velocity of P-waves increases dramatically (from about 6.5 to 8.0 km/s) at the Mohorovicic discontinuity between the Earth's crust and mantle.

See related terms: Mohorovicic discontinuity,  P-wave,  seismic wave