"Liquid paperboard" is not a standard term in the paperboard industry. It is possible that this phrase is being used in a specific context that is not clear from the question.

Here are some possible interpretations and why they might be incorrect:

* Paperboard in liquid form: Paperboard, by definition, is a rigid material. It cannot exist in a liquid form. It's possible the term is being used metaphorically to describe a product that is very thin or flexible.

* Paperboard used to package liquids: This is a more likely interpretation. Paperboard is often used to create containers for liquids, such as milk cartons, juice boxes, and food containers.

* Paperboard made from recycled liquid waste: This is a less likely interpretation. Paperboard is typically made from wood pulp, and while it may be recycled, it doesn't directly use "liquid waste" as a raw material.

To understand what "liquid paperboard" refers to, more context is needed. Could you please provide more information about where you encountered this term? For example:

* What is the source of this information?

* What is the context in which you encountered this phrase?

With more information, I can help you understand what "liquid paperboard" means in this specific context.