The Collaborative International Dictionary of English v.0.48:

Plat \Plat\, n. [Cf. Plat flat, which perh. caused this
   spelling, and Plot a piece of ground.]
   A small piece or plot of ground laid out with some design, or
   for a special use; usually, a portion of flat, even ground.
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         This flowery plat, the sweet recess of Eve. --Milton.
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         I keep smooth plat of fruitful ground.   --Tennyson.
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The Collaborative International Dictionary of English v.0.48:

Plat \Plat\, v. t.
   To lay out in plats or plots, as ground.
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The Collaborative International Dictionary of English v.0.48:

Plat \Plat\, a. [F. plat. See Plate, n.]
   Plain; flat; level. [Obs.] --Gower.
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The Collaborative International Dictionary of English v.0.48:

Plat \Plat\, adv.
   1. Plainly; flatly; downright. [Obs.]
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            But, sir, ye lie, I tell you plat.    --Rom. of R.
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   2. Flatly; smoothly; evenly. [Obs.] --Drant.
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The Collaborative International Dictionary of English v.0.48:

Plat \Plat\, n.
   1. The flat or broad side of a sword. [Obs. or Prov. Eng.]
      --Chaucer.
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   2. A plot; a plan; a design; a diagram; a map; a chart. [Obs.
      or Prov. Eng.] "To note all the islands, and to set them
      down in plat." --Hakluyt.
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The Collaborative International Dictionary of English v.0.48:

Plat \Plat\, v. t. [imp. & p. p. Platted; p. pr. & vb. n.
   Platting.] [See Plait.]
   To form by interlaying interweaving; to braid; to plait.
   "They had platted a crown of thorns." --Matt. xxvii. 29.
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The Collaborative International Dictionary of English v.0.48:

Plat \Plat\, n.
   Work done by platting or braiding; a plait.
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         Her hair, nor loose, nor tied in formal plat. --Shak.
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WordNet (r) 3.0 (2006):

plat
    n 1: a map showing planned or actual features of an area
         (streets and building lots etc.)
    v 1: make a plat of; "Plat the town" [syn: plat, plot]