The Collaborative International Dictionary of English v.0.48:

Pleat \Pleat\ (pl[=e]t), n. & v. t.
   See Plait.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pleat
    n 1: 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: pleat or gather into a ruffle; "ruffle the curtain fabric"
         [syn: ruffle, pleat]
    2: fold into pleats, "Pleat the cloth" [syn: pleat, plicate]