From The Free Forex Encyclopedia
OsMA is the abbreviation used to express a function of Oscillator within technical analysis, OsMA standing for Oscillator - Moving Average (or sometimes Oscillator - Moving Average of Oscillator.)
Oscillator itself is an indicator that allows the demonstration of the relationship between any two given set periods of the Moving Average, which may then be either expressed as a percentage or as a number. There are two forms of oscillator, the price oscillator and the volume oscillator.
Oscillator itself is a useful trend indicator and allows the discovery of short-term conditions that may have been either oversold or overbought. When the value of the oscillator begins to approach the upper extreme levels the asset can then be deemed to have been overbought, shows an example of oversell when it approaches the lower extremes.
OsMA, on the other hand allows a clear demonstration of the variance of the oscillator from its moving average, in which case the main line of the MACD then serves as the oscillator, with the signal line of the MACD becoming the moving average.