Definition of "flat"
flat1
adjective
comparative flatter, superlative flattest
(figurative) Lacking liveliness or action; depressed; uninteresting; dull and boring.
(authorship, figuratively, especially of a character) Lacking in depth, substance, or believability; underdeveloped; one-dimensional.
(horticulture, of certain fruits) Flattening at the ends.
(of measurements of time) Exact.
adverb
comparative more flat, superlative most flat
noun
plural flats
(technical, theatre, stagecraft) A rectangular wooden structure covered with masonite, lauan, or muslin, often produced in standard modules, that is used to build wall surfaces on stage. Flats can be painted and outfitted with doors and/or windows to depict a building or other part of a scene. It's a hard-surfaced alternative to a backcloth or backdrop.
verb
third-person singular simple present flats, present participle flatting, simple past and past participle flatted