Definition of 'Down Volume'
A stock volume that closes at a price lower than the previous day's close. Down volume occurs when a stock finishes a day of trading at a level lower than its open, meaning that the trading volume for the day was more bearish than bullish.
Also referred to as "down on volume."
Investopedia explains 'Down Volume'
If a stock closed at a price lower than the previous day's close, the share volume for that day would be considered down volume. Quite often market participants refer to a day of overall market down volume as a day of bearish volume, due to an overall bearish sentiment sending markets down. Typically days of down volume are more heavy in terms of overall volume than up days.