Definitions

1. adjective

growing or developing underground, especially in relation to fungi or plants

“The mycologist studied the hypogeous species of fungi that grew in the forest.”

2. adjective

underground or below the surface, especially of water or a river

“The hypogeous river flowed silently through the dark caverns.”

3. noun

a fungus that grows underground, especially of the genus Hymenopogon

“The biologist identified the hypogeous fungus in the soil sample.”