The capacity to notice thinking while it is happening, including repetition, prediction and interpretation, without having to treat every thought as instruction or evidence.
Metacognition is the capacity to notice your own thinking as thinking.
A thought can feel persuasive because it is familiar, vivid, repeated or emotionally charged. Metacognition creates a little more room around it: enough to ask what the thought is doing, what it is assuming and whether it deserves the authority it currently has.
You can hear the thought without handing it the microphone.
This capacity includes thought observation and replay awareness. The point is not to become detached from every thought. It is to recognise when the mind is solving, rehearsing, predicting, protecting or simply looping.