An "opaque container" is a type of container that you cannot see through. It means you cannot see what is inside the container because it is not transparent or clear like glass or plastic. Full definition
Use opaque containers for stuff that can be damaged by light. (styleathome.com)
It is a pump opaque container, which has an inner container inside that moves up when you use a product, this kind of mechanism shows you how much of the product is left. (keenonbeauty.com)
For example, when we put the sugary snacks in our New York office's kitchens into opaque containers, employees consumed 3.1 million fewer calories over seven weeks. (social.hays.com)