Steering Committee Definition

A group of high-level stakeholders who are responsible for providing guidance on overall strategic direction. They do not take the place of a sponsor, but help to spread the strategic input and buy-in to a larger portion of the organization. The steering committee is usually made up of organizational peers, and is the combination of direct customers and indirect stakeholders.

Other Definitions

I've also put together a description of project management fundamentals if you're interested in learning more about this profession.

References
Tom Mochal and Jeff Mochal, Lessons in Project Management