permanent press

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A chemical process in which fabrics are permanently shaped and treated for wrinkle resistance.
• noun A fabric treated by permanent press.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A characteristic of a fabric, especially one used in clothing, often created by applying a chemical treatment and pressure, which causes lasting resistance to wrinkling and retention of pleats and creases.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a fabric that has been chemically processed to resist wrinkles and hold its shape