from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Located under the earth's surface; underground.
- adj. Botany Of or relating to seed germination in which the cotyledons remain below the surface of the ground.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. existing or growing underground
from The Century Dictionary and Cyclopedia
- Subterranean; underground; in botany, growing beneath the surface of the earth, as parts of plants, or in a few instances entire plants, as the truffle and the tuckahoe. Also hypogeous, hypogæous, hypogean, hypogæan.
From Latin hypogēus, from Greek hupogeios : hupo-, hypo- + gē, earth.(American Heritage® Dictionary of the English Language, Fourth Edition)
hypo- + -geal (Wiktionary)