Floor price is the lowest limit price where a stock can be traded in a day. It is 50% lower from the previous price.


Update: In May 2020, SEC likewise approved the adjustment of the lower static threshold or pricing band from 50% to 30% as another tool to contain the expected high volatility in capital markets, while the upper threshold of 50% remains unchanged.   


Example:


The lowest price the stock may reach for the day is 8.0500.  This stock's price cannot go lower than 8.0500.