Churn Rate:

In the marketing world, churn rate refers to the number of customers that discontinue service in a given time period.  This applies to subscription-based services more than others because that business model thrives on recurring billing.  If the churn rate is high it means the CLV is lower and there is a greater demand on new acquisitions.  If the churn rate is lower than the rate of acquisition, then it is like a snowball, building more recurring revenue month after month.