from
The Collaborative International Dictionary of English v.0.48
Basement \Base"ment\ (b[=a]sment), n. [F. soubassement. Of
uncertain origin. Cf. {Base}, a., {Bastion}.] (Arch.)
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.
[1913 Webster]
{Basement membrane} (Anat.), a delicate membrane composed of
a single layer of flat cells, forming the substratum upon
which, in many organs, the epithelioid cells are disposed.
[1913 Webster]