Yikes. Let me give one possible definition, originally from Stimpson J. Cat. It's a sort of scientific naturalism approach.
Definition 1: The term "real" is defined to refer to everything which has any kind of effect on something else which is real. This self-referential definition is completed with the definition that I am real.
Definition 2: The term "physical" is defined to refer to anything which is, in principle, observable.
Now we need an axiom that says that real things are logical and consistent:
Axiom 1: Everything real can be described according to some set of consistent logical rules.
Now we need a useful epistemology that allows us to determine natural laws:
Axiom 2: The natural laws describing real events can be determined through observation of the effects those events have.
If axioms 1 and 2 are correct, then anything that can meaningfully be said to exist (a real thing) is physical.
~~ Paul