From The Collaborative International Dictionary of English v.0.48:
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]
From The Collaborative International Dictionary of English v.0.48:
Flatting \Flat"ting\, n. 1. The process or operation of making flat, as a cylinder of glass by opening it out. [1913 Webster]
2. A mode of painting,in which the paint, being mixed with turpentine, leaves the work without gloss. --Gwilt. [1913 Webster]
3. A method of preserving gilding unburnished, by touching with size. --Knolles. [1913 Webster]
4. The process of forming metal into sheets by passing it between rolls. [1913 Webster]
Flatting coat, a coat of paint so put on as to have no gloss.
Flatting furnace. Same as flattening oven, under Flatten.
Flatting mill. (a) A rolling mill producing sheet metal; esp., in mints, the mill producing the ribbon from which the planchets are punched. (b) A mill in which grains of metal are flatted by steel rolls, and reduced to metallic dust, used for purposes of ornamentation. [1913 Webster]