hypogeal

adjective

1. of, or occurring in, the region below the surface of the earth
2. 1. Bot. growing or maturing underground, as peanuts or truffles: said esp. of cotyledons
   2. Zool. burrowing, living, or developing beneath the ground, as certain insect larvae

Origin: < LL hypogeus, underground (< Gr hypogaios < hypo-, under + gē, earth) + -al