Relating to or characteristic of apathism or apathists; emphasizing or advocating emotional detachment and indifference.
From 'apathist' (one who practices apathism) plus the adjective suffix '-ical,' describing things related to apathist philosophy or practice.
The fact that English can add '-ical' to almost any noun (apathist → apathistical) shows how flexible the language is, even if this particular word is quite rare.
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