A crawlspace is an area of limited height under a building's floorboards that serves as a foundation. Synonyms for the term are "cellar," "basement," "underground area," and "sub-basement." "Cavity," "substructure," "lair," "tunnel," "underspace," and "pit" are all also words that can be used to describe a crawlspace. Crawlspace entrances can also be called "hatches," "trap doors," or "access points." These words can be useful when describing particular characteristics of a crawlspace or when discussing building exteriors or blueprints. Overall, there are many synonyms available, each with a slightly different connotation and context in which they can be used.