Hypogean is a term used to describe organisms or objects that live or grow underground. Some synonyms for hypogean include subterranean, underground, subterraneous, buried, hidden, and sunken. Subterranean refers specifically to the area beneath the earth's surface, while underground can also encompass structures such as tunnels or basements. Subterraneous and buried both imply being covered or hidden beneath the ground. Hidden and sunken both suggest being out of sight or hidden beneath the surface. Using synonyms for words like hypogean can add variety and interest to your writing, while also helping readers better understand your meaning.