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Describing an average in which some values count for more than others. For example, if an index consisting of 10 stocks is weighted for price, this means that the average price of the stocks will move more when the stocks with higher price move. Most indices use weighted averages so "smaller" values do not affect the index inordinately. This helps correct for the fact that averages tend to be affected by extreme values. One of the most common ways of weighting an average is to weight for market capitalization.