[sub.stra.tum] n, pl -stra.ta [ML, fr. L, neut. of substratus, pp. of substernere to spread under, fr. sub- + sternere to spread--more at strew] (1631): an underlying support: foundation: as a: substance that is a permanent subject of qualities or phenomena b: the material of which something is made and from which it derives its special qualities c: a layer beneath the surface soil; specif: subsoil d: substrate
2.