Gearing is the term used in Britain and much of the Commonwealth for leverage: the extent to which a company or investor uses borrowed money rather than its own capital. The full explanation is on the Leverage page.
A common measure is the gearing ratio, usually net debt divided by shareholders' equity, taken from the balance sheet. Highly geared firms earn more for shareholders in good times but are more exposed when profits fall or interest rates rise; buyouts financed this way are described under leveraged buyout.