Overhang

What Does Overhang Mean?
A measure of the potential dilution to which a common stock's existing shareholders are exposed due to the potential that stock-based compensation will be awarded to executives, directors or key employees of the company. It is usually represented in percentage form and is calculated as stock options granted, plus the remaining options that have yet to be granted divided by the total shares outstanding.

Investopedia explains Overhang
There is no precise rule-of-thumb for determining what level of options overhang is bad for investors but, generally speaking, the higher the number, the greater the risk. If a company has a very high options overhang, it must generate even higher levels of growth in order to provide decent returns to investors net of the overhang's dilutive effects on investor returns.