Hypogeous is an adjective that describes things that are underground or grow beneath the surface of the ground. Other synonyms for this word include subterranean, subterraneous, and underground. These words can be used to describe plant structures like mushrooms or roots, as well as animals like moles or earthworms that live underground. Other words that can be used interchangeably with hypogeous include buried, hidden, concealed, and obscured. While these words generally have similar meanings, they each carry slightly different connotations that may be more appropriate for certain situations. Overall, hypogeous is a useful word that helps us describe the hidden world that exists beneath our feet.