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]