Definition of "subterranean" [sub•ter•ra•ne•an]

• Situated or operating beneath the earth's surface; underground. (adjective)
• Hidden; secret: subterranean motives for murder. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Just like in subterranean carbon sequestration, the CO2 would be pumped and moved via pipes to the bag."
• "Although the opinion is silent on the issue, it is safe to assume that the released men are college Professors holding doctorates in subterranean climatology."
• "Or bound in subterranean dungeons [Maurer]. prison-houses -- either literal prisons, or their own houses, whence they dare not go forth for fear of the enemy."