subterraneous s being or operating under the surface of the earth s lying beyond what is openly revealed or avowed (especially being kept in the background or deliberately concealed) Usage(s) They practice husbandry and agriculturesome species keep herds of aphids and others grow subterraneous gardens of fungi. But from some of its subterraneous horror he shies off, some of it eludes him, and the rest comes through merely as melodrama. They practice husbandry and agriculturesome species keep herds of aphids and others grow subterraneous gardens of fungi. Synonym(s) subterranean ulterior