What is IP2?

The Second Order Intercept Point (IP2) is a hypothetical point where the power of second order components will reaches the same level as the power of the fundamental components. 

So, if we draw the power input versus power output, IP2 is an interpolated point where the fundamental component power curve meets the second order intermodulation (IMD2) component curve.

This is similar to IP3, however of less concern as the second order intermodulation products are located at frequencies which can easily be filtered out. If the results will be analyzed on spectrum analyzer, the frequency components will look as shown in the figure below.