1. n. [Geology]

A geological surface that separates younger overlying sedimentary strata from eroded igneous or metamorphic rocks and represents a large gap in the geologic record.

See related terms: angular unconformity,  basement,  conformable,  conformable,  disconformity,  erosion,  erosion,  geologic time scale,  igneous,  metamorphic,  stratum,  unconformity