A security that is not considered active in trading. In other words, the trading activity and turnover of an inactive security tend to be less than a minimum level (e.g., 500 or 1000 per day, etc.)

Activity and inactivity are not defined in isolation of a market and the norms of trading. Many securities many not be traded daily, while others may not have more than one quote a month. Activity or inactivity depends on multiple factors including trading days, trading volume within a day, etc.

From the perspective of collateral (loan) value, a security that is traded every day may be viewed as active, while the number of units traded (trading volume) determines how active its trading is. From a market standpoint, a security would be active if a minimum number of units is traded every day (e.g., 20,000 or 50,000), otherwise it would be  perceived as inactive.