What is another word for "flat"?

Roget's Thesaurus (1911) lists these synonyms for "flat": abeyance, accubation, accumbent, adown, alkali, all, alluvial, amateur, and, area, ass, awkward, azimuth, back, bad, bait, basement, basin, beam, below, beneath, bilge, billiard, bite, bland, blandness, blanket, blunderer, blunderhead, blunt, board, book, boring, bowling, bungler, bush, butte, calm, campagna, campestral.