the ability and tendency to determine what should be done and to start doing it without instruction
to start something
The exact meaning of starting something depends upon the context. For example:
"She did it on her own initiative." — started it without anyone telling her to
"She seized the initiative." — started actions that force others to react to her rather than her having to react to them
"the peace initiative" — a plan or the start of actions to bring about something
"a ballot initiative" — a proposed law that is started by citizen petition rather than by the legislature (applicable in many jurisdictions such as California)
It proved that the only problems which America had to face were Mormonism and Prohibition: "Don't let any of these self-conceited fellows that are always trying to stir up trouble deceive you with the belief that there's anything to all these smart-aleck movements to let the unions and the Farmers' Nonpartisan League kill all our initiative and enterprise by fixing wages and prices.
Chapter 28 (27% in)
There are no more uses of "initiative" in Main Street.