Flat \Flat\, v. t. [imp. & p. p. {Flatted}; p. pr. & vb. n. {Flatting}.] 1. To make flat; to flatten; to level. [1913 Webster] 2. To render dull, insipid, or spiritless; to depress. [1913 Webster] Passions are allayed, appetites are flatted. --Barrow. [1913 Webster] 3. To depress in tone, as a musical note; especially, to lower in pitch by half a tone. [1913 Webster]