My definition of matter is that it is everything. Besides anti atoms, everything is made up of atoms, which we call matter. Matter is made into three parts: solid, liquid, gas, and plasma. Therefore, matter is everything.
I came up with this definition because Mr. Solarz told us that the 4 sections are all matter. In fact, everything is matter. So if I point to something, it's matter. That is why everything is matter.
Scientists define matter as three categories. Solid, liquid and gas. Plasma is not a main category. Everything falls in these sections and are described as matter.