What does Acetate (also Triacetate) mean?

Fabrics made from acetate have a high luster, fair absorbency, and are even noted to be used in airplane wings in World War I.  The synthetic material is known for poor abrasion resistance, low tolerance to the sun, and low strength which shrinks up to 30% when wet.

Heddels explains Acetate (also Triacetate)

As acetate is a synthetic (i.e. unnatural) fibre that abrades easily, wrinkles easily, and shrinks drastically, acetate garments are delicate and must be dry cleaned.  In terms of raw denim, do not purchase raw denim that is cotton woven with acetate, unless you are intentionally looking for this sort of denim.