pleat 
(plēt)
(plēt)n.
A fold, especially one of several parallel folds made by doubling cloth or other material on itself and then pressing or stitching it into place.
tr.v. pleat·ed, pleat·ing, pleats
To press or arrange in pleats: pleat a skirt; pleat curtains.
[Middle English plet, variant of plait, pleat, fold; see PLAIT.]
pleater n.