The Collaborative International Dictionary of English v.0.48:

Plait \Plait\, n. [OE. playte, OF. pleit, L. plicatum, plicitum,
   p. p. of plicare to fold, akin to plectere to plait. See
   Ply, and cf. Plat to weave, Pleat, Plight fold.]
   1. A flat fold; a doubling, as of cloth; a pleat; as, a box
      plait.
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            The plaits and foldings of the drapery. --Addison.
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   2. A braid, as of hair or straw; a plat.
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   Polish plait. (Med.) Same as Plica.
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The Collaborative International Dictionary of English v.0.48:

Plica \Pli"ca\, n. [LL., a fold, fr. L. plicare to fold. See
   Ply, v.]
   1. (Med.) A disease of the hair (Plica polonica), in which it
      becomes twisted and matted together. The disease is of
      Polish origin, and is hence called also Polish plait.
      --Dunglison.
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   2. (Bot.) A diseased state in plants in which there is an
      excessive development of small entangled twigs, instead of
      ordinary branches.
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   3. (Zool.) The bend of the wing of a bird.
      [1913 Webster] Plicate