Some describe it as a fourth state of matter.
What is plasma?
Instead of a definition, here is an explanation, of sorts:
As you raise the temperature of any material, the molecules become so
energetic that they break apart, and eventually,when the temperature is high
enough, even the atoms (ions) dissociate into electrons and protons. This
broken-up gassy material is plasma.
So, if you take the liquid part of blood or milk, and get it very hot, you
are changing plasma to plasma :-)