subter-

(Latin: under, beneath, secretly, less than; formed from sub-)

subterannuating
subterannuation
subterfuge (s) (noun), subterfuges (pl)
subterraneal
Subterranean.
subterranean
1. Situated or operating beneath the earth's surface; underground.
2. Hidden; secret; such as, subterranean motives for murder.
subterraneous
1. Being or lying under the surface of the earth; situated within the earth, or under ground; as, subterraneous springs; a subterraneous passage.
2. Lying beyond what is openly revealed or avowed (especially being kept in the background or deliberately concealed); such as, subterraneous motives for murder.
subterrestrial
Underground; subterranean.