Having an even and horizontal surface, or nearly so, without prominences or depressions; level without inclination; plane. Though sun and moon Were in the flat sea sunk. Milton. Lying at full length, or spread out, upon the ground; level with the ground or earth; prostrate; as, to lie flat on the ground; hence, fallen; laid low; ruined; destroyed. What ruins kingdoms, and lays cities flat! Milton. I feel . . . my hopes all flat. Milton. Wanting relief; destitute of variety; without points of prominence and striking interest. A large part of the work is, to me, very flat. Coleridge. Tasteless; stale; vapid; insipid; dead; as, fruit or drink flat to the taste. Unanimated; dull; uninteresting; without point or spirit; monotonous; as, a flat speech or composition. How weary, stale, flat, and unprofitable Seem to me all the uses of this world. Shak. Lacking liveliness of commercial exchange and dealings; depressed; dull; as, the market is flat. Clear; unmistakable; peremptory; absolute; positive; downright. Flat burglary as ever was committed. Shak. A great tobacco taker too, -- that's flat. Marston. Below the true pitch; hence, as applied to intervals, minor, or lower by a half step; as, a flat seventh; A flat. Not sharp or shrill; not acute; as, a flat sound. Sonant; vocal; -- applied to any one of the sonant or vocal consonants, as distinguished from a nonsonant (or sharp) consonant. Flat arch. (Arch.) See under Arch, n., 2. (b). -- Flat cap, cap paper, not folded. See under Paper. -- Flat chasing, in fine art metal working, a mode of ornamenting silverware, etc., producing figures by dots and lines made with a punching tool. Knight. -- Flat chisel, a sculptor's chisel for smoothing. -- Flat file, a file wider than its thickness, and of rectangular section. See File. -- Flat nail, a small, sharp-pointed, wrought nail, with a flat, thin head, larger than a tack. Knight. -- Flat paper, paper which has not been folded. -- Flat rail, a railroad rail consisting of a simple flat bar spiked to a longitudinal sleeper. -- Flat rods (Mining), horizontal or inclined connecting rods, for transmitting motion to pump rods at a distance. Raymond. -- Flat rope, a rope made by plaiting instead of twisting; gasket; sennit.