Noah Webster's Dictionary (n.) The outer wall of the ground story of a building, or of a part of that story, when treated as a distinct substructure. ( See Base, n., 3 (a).) Hence: The rooms of a ground floor, collectively.

Multi-Version Concordance Basement (1 Occurrence) Ezekiel 41:8 I saw also that the house had a raised basement round about: the foundations of the side-chambers were a full reed of six great cubits. (ASV JPS)