A rainmaker is any person who brings clients, money, or respect to an organization based solely on his or her association. Traditionally, the term "rainmaker" applied to members of the legal profession, like attorneys-turned-politicians who retired from public life (forcibly or otherwise) and went on to practice law at nationally-recognized firms.

Over time, the term gained usage in many other industries and activities, including investment banking, political campaigning and public speaking. For example, former U.S. Vice President Al Gore's association with the environmental movement caused numerous venture capital firms to add Gore as a partner in hopes that his "rainmaking" abilities would help them raise hundreds of millions of dollars for alternative energy initiatives.

In everyday usage, the term "rainmaker" can apply to anyone - from the salesperson who always finishes first in sales to the engineer who consistently finds innovative ways to present a company's products. In the purest sense, a rainmaker is a difference maker.

This question was answered by Justin Bynum.