1. (p. pr. & vb. n.) of Underpin.

2. (n.) The act of one who underpins; the act of supporting by stones, masonry, or the like.

3. (n.) That by which a building is underpinned; the material and construction used for support, introduced beneath a wall already constructed.

4. (n.) The foundation, esp. of a frame house.

base basement basis bearing wall bed bedding bedrock brace buttress column floor flooring fond footing foundation fundament fundamental ground grounds groundwork hardpan infrastructure pavement principle prop radical riprap rock bottom root rudiment seat seating shore sill solid ground solid rock stay stereobate stylobate substratum substruction substructure terra firma underbuilding undercarriage undergirding understruction understructure