The definition of active is absolutely not fuzzy. Standard metrics include 1, 7 and 30 day actives, i.e. the number of people who have logged in at least once i

The definition of active is absolutely not fuzzy. Standard metrics include 1, 7 and 30 day actives, i.e. the number of people who have logged in at least once in the last N days. Tracking those three over time gives you some good statistics.