I just Googled "insanity" — Insanity® has been trademarked and repurposed:
"Buy INSANITY® from the Official Beachbody site. 60-day Money-Back Guarantee.
I was looking for the 'dictionary definition' and it's pretty vague: insanity is a "state of being
seriously mentally ill"; the usual synonyms apply: "mental illness, madness, dementia; lunacy, instability, mania, psychosis."
Insanity usually implies a "break with reality"—still vague, but "I know it when I see it." It's all been pathologized, of course, each shade of madness has a number.
It's all sort of relative, isn't it? In a way, we're all a bit insane, traumatized by an insidious capitalist-consumer techno-fascistic society. Functional integration in the system could be called a "functional insanity" and serve as a baseline, an acceptably low-level dementia, readily treated with a little hard work and the appropriate pharmeceutical drugs.
Deviations from the functional baseline comprise the spectrum of accepted clinical disorders—crazy, mad, looney tunes, schizophrenic, total nut case, psychotic and, perhaps the most severe form of mental illness, Trump supporter.
A rising sanity baseline may, in the future, redefine insanity as we know it. Marketing studies indicate that insanity can be eliminated altogether by 2025 if consumers buy a sufficient quantity of bodybuilding products.
Personal experience: insane on one occasion for 3 or 4 hours while on PCP.

(Edited to replace "relevant" with "relative")