The dictionary has a pretty simple and spot-on definition for Pomace. Lets take a look:
"The dry or pulpy residue of material (such as fruit, seeds, or fish) from which a liquid (such as juice or oil) has been pressed or extracted. 2 : something crushed to a pulpy mass." Source
Like I said, it's pretty spot on. When it comes to olives, the pomace is the remaining pulp or the solids of the olive fruit, skin and pit after the initial oil has been crushed and spun. This initial crushing and spinning process produces the higher grades of extra virgin and virgin olive oils.
But pomace doesn't only exist with olives. You can also have pomace made up of the remains of grapes after making wine, and pomace of lots of other types of fruit.
So what is Pomace Olive Oil? It's the oil made from the pomace of the olive. This is the lowest grade of olive oil, and is also the cheapest. We have a lot of resources where you can learn more about the process of how it's made and what it's good for. Check out the articles below!
People call the oil made from pomace "Olive Pomace Oil", "Pomace Oil" or "Pomace Olive Oil". This is generally understood what they are talking about, and you will see people in this oil industry use all different terms.
That said, the term is technically recognized only as the grade "Olive Pomace Oil" by the USDA with the wording in that particular order.
Want to learn more? Check out Olive Pomace Oil: The Ultimate Guide for a deep dive on everything Olive Pomace Oil.