What defines a false alarm in the context of a security system?

A false alarm within the context of a security system is specifically defined as an activation that occurs without any actual intrusion taking place. This means that the alarm system is triggered by something that is not a legitimate security breach, such as an environmental factor, a malfunction, or other benign causes, rather than an unauthorized entry or threat.

When considering the other options, the definition of a false alarm does not encompass all forms of alarm activations, since some activations may indeed be valid alarms indicating real threats. Furthermore, the notion of false alarms isn't limited to alarms that are ignored; these can still be legitimate threats that require attention. Lastly, while certain alarm systems may register activations from pets, the critical issue with false alarms is that they occur without any actual intrusion, making only the presence of a legitimate security threat the distinct factor. Therefore, option B accurately captures the essence of a false alarm as it relates to security systems.