[ beys-muh nt ]
/ ˈbeɪs mənt /


a story of a building, partly or wholly underground.
(in classical and Renaissance architecture) the portion of a building beneath the principal story, treated as a single compositional unit.
the lowermost portion of a structure.
the substructure of a columnar or arched construction.

Origin of basement

First recorded in 1720–30; base1 + -ment Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for basement

/ (ˈbeɪsmənt) /


  1. a partly or wholly underground storey of a building, esp the one immediately below the main floorCompare cellar
  2. (as modifier)a basement flat
the foundation or substructure of a wall or building
geology a part of the earth's crust formed of hard igneous or metamorphic rock that lies beneath the cover of soft sedimentary rock, sediment, and soil
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012