Most Active

What Does Most Active Mean?
The stocks on an exchange that had the highest volume over a given period. The most common time period used is a single trading day.

Investopedia explains Most Active
Generally, most-active stocks are those with the most shares traded over one day.  Usually, stocks experience higher-than-normal trading volume due to significantly important new information affecting the stock reaching the market. This creates a strong impetus amongst investors to either buy or sell the stock, resulting in heavier trading volume, and often strong momentum in the stock as well.