Harmonic Average
The mean of a set of positive variables. Calculated by dividing the number of observations by the reciprocal of each number in the series.
Investopedia Commentary
Alternately, the harmonic average could be thought of as the reciprocal of the arithmetic mean of inverse values.
Also known as harmonic mean.
See also: Arithmetic Mean Average, Fixed-Charge Coverage Ratio, Price-Earnings Ratio - P/E