Definition of "subbasement" []

• A floor beneath a main basement of a building. (noun)

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.

• "These included the Manhattan Project and housing the 'Arsenal' robots in a hidden subbasement in his mansion."
• "For all the horrors you hear about Congress's poisoned atmosphere—its paralysis, its subbasement approval ratings—the handsome marble hallways, filled with American flags, still gleam; wide-eyed constituents still travel them; and it's still hard not to find yourself with something resembling a lump in your throat."
• "Three years after the crisis began with a burp in the subprime subbasement, these questions elicit scant consensus."