underpinning (root: underpin)

• POS: Noun
• HYPHEN: un=der=pin=ning

CIDE DICTIONARY

underpinning, n. 

•  The act of one who underpins; the act of supporting by stones, masonry, or the like.  [1913 Webster]
•  That by which a building is underpinned; the material and construction used for support, introduced beneath a wall already constructed.  [1913 Webster]

THESAURUS

underpinning

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