1. In the context of inbound call centers, an abandoned call is a call from someone who hung up while waiting to be served by an agent (presumably because he or she had to wait too long on hold).
2. In an outbound context an abandoned call is a call dialed by the predictive dialer that no agent was available to take. This is sometimes referred to as a nuisance call because the called party gets hung up on the instant he or she answers the phone. For this reason, many local authorities have mandated maximum rates for outgoing abandoned calls. Typically these mandated rates are around 5 percent.
Note: Statistics reported for abandoned calls include the number of calls abandoned in a given time period or by a given agent group (this hour, this shift, this month, etc.), or the percentage of the total number of calls taken that are abandoned (the "rate" or abandonment rate).
The label "abandoned calls" is sometimes shortened to ABAN or ABN in places where space is at a premium (such as call center readerboard systems).