To answer you question as to definition, I'm not sure and I don't have a problem with that. It has something to do with goal directed behavior and an availability of assumable states to achieve a reasonable subset of those goals.
From "Gravitation" By Wheeler, Thorne and Misner:
Here and elsewhere in science, as stressed not least by Henri Poincare, that view is out of date which used to say, "Define your terms before you proceed." All the laws and theories of physics, including the Lorentz force law, have this deep and subtle character, that they both define the concepts they use and make statements about these concepts. Contrariwise, the absence of some body of theory, law and principle deprives one of the means properly to define or even to use concepts. Any forward step in human knowledge is truly creative in this sense: that theory, concept, law, and method of measurement - forever inseparable-are born into the world in union.
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