The Collaborative International Dictionary of English v.0.48:

Plait \Plait\, v. t. [imp. & p. p. Plaited; p. pr. & vb. n.
   Plaiting.]
   1. To fold; to double in narrow folds; to pleat; as, to plait
      a ruffle.
      [1913 Webster]

   2. To interweave the strands or locks of; to braid; to plat;
      as, to plait hair; to plait rope.
      [1913 Webster]

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.
      [1913 Webster]

            The plaits and foldings of the drapery. --Addison.
      [1913 Webster]

   2. A braid, as of hair or straw; a plat.
      [1913 Webster]

   Polish plait. (Med.) Same as Plica.
      [1913 Webster]

WordNet (r) 3.0 (2006):

plait
    n 1: a hairdo formed by braiding or twisting the hair [syn:
         braid, plait, tress, twist]
    2: any of various types of fold formed by doubling fabric back
       upon itself and then pressing or stitching into shape [syn:
       pleat, plait]
    v 1: make by braiding or interlacing; "lace a tablecloth" [syn:
         braid, lace, plait]
    2: weave into plaits; "plait hair"

Moby Thesaurus II by Grady Ward, 1.0:

108 Moby Thesaurus words for "plait":
   accordion pleat, box pleat, braid, bun, chignon, coat, coating,
   coil, collop, covering, crease, crimp, crisp, cue, cut, deal, disk,
   dog-ear, double, double over, enfold, enlace, entwine, feuille,
   film, flap, flounce, flute, foil, fold, fold over, frill, gather,
   infold, interfold, interknit, interlace, intertie, intertissue,
   intertwine, intertwist, interweave, intort, knife pleat, knit,
   knot, lace, lamella, lamina, laminated glass, laminated wood, lap,
   lap over, leaf, loom, loop, mat, membrane, net, noose, pane, panel,
   patina, peel, pellicle, pigtail, plank, plat, plate, plating,
   pleach, pleat, plicate, ply, plywood, queue, quill, raddle, rasher,
   rattail, ruff, ruffle, safety glass, scum, sheet, skin, slab, slat,
   slice, splice, table, tablet, tail, tissue, topknot, tuck,
   turn over, twill, twine, twist, veneer, wafer, wattle, weave, web,
   wreath, wreathe, wreathwork