Wool? Or cotton?

Wash in hot water, dry on high heat.

Synthetic wool. And to shrink it to a much lesser degree than what a dryer on high would do to it, I should have mentioned.

Synthetics tend not to shrink. You may have to alter.

I think the dryer is the only way to shrink clothes. Why not dry it for a while and then pull it our to see if you’ve gotten the shrinkage you want?

@canidmajor Alter how?
@janbb Good idea.

By the way, if boiling hot water is what stretched it, should ice cold water reverse it?
It’s not my clothing item.

Alter by sewing. Adjusting seams and so forth.

It’s irregularly stretched.

Ask this as a question to Google. Specify that the fabric is synthetic. Something along the lines of “How do I restore the original shape of a synthetic knitted garment?” Or somesuch. You will get results from a number of different sources, some of them might be helpful.

@canidmajor Thanks good idea.
I got an Activity For You today for the spam above, but probably not for your last post.