subterranean, adj.
lying beyond what is openly revealed or avowed (especially being kept in the background or deliberately concealed)
<adj.all>
subterranean subterraneous ulterior
sample sentences
"subterranean motives for murder""looked too closely for an ulterior purpose in all knowledge"- Bertrand Russell
semantic pointers
similar to
being or operating under the surface of the earth
<adj.all>
subterranean subterraneous
sample sentences
"subterranean passages""a subsurface flow of water"
semantic pointers
similar to