Foundation  n. 1 a solid ground or base beneath a building. B (usu. In pl.) Lowest part of a building, usu. Below ground level. 2 material base. 3 basis, underlying principle. 4 a establishing (esp. An endowed institution). B college, hospital, etc. So founded; its revenues. 5 (in full foundation garment) woman's supporting undergarment, e.g. A corset. [latin: related to *found2]