Sweaters that don't cinch at the bottom

Sweaters that don't cinch at the waist. You know, hang looser.

What do you call them for, say, online shopping?

Try "men's loose sweaters" on the Google, which gets pictures of what I think you're looking for.

or open bottom, floating bottom.

Open hem?

Just make sure the description does not say "banded"  or "cinched" or "tied."   Loose fit is also a good one to look for.  Is there a specific catalog you are looking at?