underground(below the surface of the ground • underground railways; underground streams); chthonian; under-earth; subway; hypogean; hypogeous; belowground; subterranean(lying, situated or constructed underground • subterranean passages); miny; below the ground(UFO researcher Scott C. Waring writes that it appears to be "too powerful of a glow to be any type of known aircraft and it's just sitting there as if it came from a tunnel from below the ground from a deep alien base."coasttocoastam.comART Vancouver)
