Ask twenty people and you will get twenty different answers. And when a definition has no common understanding it loses any and all value. Much like the master theories of economics upon which those definitions proclaim to depend.
Classical economics and its many derivatives sold as new, are simply voodoo science. They fail to deliver an accurate proxy of the evolution of mankind and therefore fail to deliver insight and foresight in human performance.
We must reinvent economics to become a reliable proxy of the evolution of mankind, subjugated to a new operating system for humanity.