Source : Webster's Revised Unabridged Dictionary (1913)

Flat \Flat\, a. [Compar. {Flatter}; superl. {Flattest}.] [Akin
   to Icel. flatr, Sw. flat, Dan. flad, OHG. flaz, and AS. flet
   floor, G. fl["o]tz stratum, layer.]
   1. 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.

   2. 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.

   3. (Fine Arts) Wanting relief; destitute of variety; without
      points of prominence and striking interest.

            A large part of the work is, to me, very flat.
                                                  --Coleridge.

   4. Tasteless; stale; vapid; insipid; dead; as, fruit or drink
      flat to the taste.

   5. 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.

   6. Lacking liveliness of commercial exchange and dealings;
      depressed; dull; as, the market is flat.

   7. Clear; unmistakable; peremptory; absolute; positive;
      downright.

            Flat burglary as ever was committed.  --Shak.

            A great tobacco taker too, -- that's flat.
                                                  --Marston.

   8. (Mus.)
      (a) Below the true pitch; hence, as applied to intervals,
          minor, or lower by a half step; as, a flat seventh; A
          flat.
      (b) Not sharp or shrill; not acute; as, a flat sound.

   9. (Phonetics) 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.

   Note: Some flat hoisting ropes, as for mining shafts, are
         made by sewing together a number of ropes, making a
         wide, flat band. --Knight.

   {Flat space}. (Geom.) See {Euclidian space}.

   {Flat stitch}, the process of wood engraving. [Obs.] -- {Flat
   tint} (Painting), a coat of water color of one uniform shade.
      

   {To fall flat} (Fig.), to produce no effect; to fail in the
      intended effect; as, his speech fell flat.

            Of all who fell by saber or by shot, Not one fell
            half so flat as Walter Scott.         --Lord
                                                  Erskine.

Cap \Cap\, n. [OE. cappe, AS. c[ae]ppe, cap, cape, hood, fr. LL,
   cappa, capa; perhaps of Iberian origin, as Isidorus of
   Seville mentions it first: ``Capa, quia quasi totum capiat
   hominem; it. capitis ornamentum.'' See 3d {Cape}, and cf. 1st
   {Cope}.]
   1. A covering for the head; esp.
      (a) One usually with a visor but without a brim, for men
          and boys;
      (b) One of lace, muslin, etc., for women, or infants;
      (c) One used as the mark or ensign of some rank, office,
          or dignity, as that of a cardinal.

   2. The top, or uppermost part; the chief.

            Thou art the cap of all the fools alive. --Shak.

   3. A respectful uncovering of the head.

            He that will give a cap and make a leg in thanks.
                                                  --Fuller.

   4. (Zo["o]l.) The whole top of the head of a bird from the
      base of the bill to the nape of the neck.

   5. Anything resembling a cap in form, position, or use; as:
      (a) (Arch.) The uppermost of any assemblage of parts; as,
          the cap of column, door, etc.; a capital, coping,
          cornice, lintel, or plate.
      (b) Something covering the top or end of a thing for
          protection or ornament.
      (c) (Naut.) A collar of iron or wood used in joining
          spars, as the mast and the topmast, the bowsprit and
          the jib boom; also, a covering of tarred canvas at the
          end of a rope.
      (d) A percussion cap. See under {Percussion}.
      (e) (Mech.) The removable cover of a journal box.
      (f) (Geom.) A portion of a spherical or other convex
          surface.

   6. A large size of writing paper; as, flat cap; foolscap;
      legal cap.

   {Cap of a cannon}, a piece of lead laid over the vent to keep
      the priming dry; -- now called an apron.

   {Cap in hand}, obsequiously; submissively.

   {Cap of liberty}. See {Liberty cap}, under {Liberty}.

   {Cap of maintenance}, a cap of state carried before the kings
      of England at the coronation. It is also carried before
      the mayors of some cities.

   {Cap money}, money collected in a cap for the huntsman at the
      death of the fox.

   {Cap paper}.
      (a) A kind of writing paper including flat cap, foolscap,
          and legal cap.
      (b) A coarse wrapping paper used for making caps to hold
          commodities.

   {Cap rock} (Mining), The layer of rock next overlying ore,
      generally of barren vein material.

   {Flat cap}, cap See {Foolscap}.

   {Forage cap}, the cloth undress head covering of an officer
      of soldier.

   {Legal cap}, a kind of folio writing paper, made for the use
      of lawyers, in long narrow sheets which have the fold at
      the top or ``narrow edge.''

   {To set one's cap}, to make a fool of one. (Obs.) --Chaucer.

   {To set one's cap for}, to try to win the favor of a man with
      a view to marriage. [Colloq.]

Source : WordNet®

flat cap
     n : a flat woolen cap with a stiff peak [syn: {cloth cap}]