Dissociation
Dissociation is a sense of disconnection from your body, your surroundings, or yourself.
Dissociation describes a range of experiences that share one feature: some part of ordinary connection drops away. People report feeling detached from their body, watching themselves from outside, finding the room unreal or far off, or losing the thread of time.
It sits on a spectrum, from mild daydreaming through to stronger states that some people describe during intense experiences. It is common enough that clinicians have standard ways of measuring it during a session, which is worth knowing on its own. An experience with a name and a scale is not, by definition, an emergency.
Between sessions it matters mostly because of what people conclude about it afterwards. Frightening and unfamiliar is easy to read as damaging. Being able to describe what happened in plain words makes it far easier to bring to a care team, and much harder to carry alone.
Intensity varies a great deal, and so does what it means for any individual. Dissociation that persists or distresses you is something to raise with your own clinician rather than something to interpret by yourself.