Un"der*pin`ning (?), n.
1.
The act of one who underpins; the act of supporting by stones, masonry, or the like.
2. Arch. (a)
That by which a building is underpinned; the material and construction used for support, introduced beneath a wall already constructed.
(b)
The foundation, esp. of a frame house.
[Local, U.S.]
© Webster 1913.