Glossary definition of 'Polarity'(Voltage) Whether a potential is positive or negative with respect to some reference or whether a parameter is proportional or inversely proportional to another.
Polarity is sometimes referred to as "absolute phase", although this is something of a contradiction in terms since phase is always relative. It is also not very helpful as polarity is not the same as phase. Whereas phase is to do with a progression through a periodic function, polarity is to do with a binary property such as north or south of a magnet, positive or negative charge or being proportional or inversely proportional. Having said that, the phase difference between a sinusoidal signal with positive polarity and the same waveform with negative polarity is 180 degrees. This is not true of all periodic functions, only symmetrical ones.
The "phase reversal" switches on audio consoles and microphone pre-amplifiers actually inverts the polarity. Using such a switch changes the relationship between the acoustic pressure and the voltage from being proportional to inversely proportional: in one instance, a positive pressure on the microphone causes a positive voltage in the console, in the other the same positive pressure causes a negative voltage.