n. See underlye.To lie in a position directly beneath.To lie under or beneath; be situated under; specifically, in geology, to occupy a lower position than, or to pass beneath: said of stratified rocks over which other rocks are spread out.To be at the basis of; form the foundation of.To lie under, in a figurative sense; be subject to; be liable to answer, as a charge or a challenge.n. In mining, same as underlay, 1.