Webster's Revised Unabridged Dictionary · 1913

Insanity

Insanity , noun

[Latin insanitas unsoundness; compare insania insanity, French insanite.]

1.
The state of being insane; unsoundness or derangement of mind; madness; lunacy.
All power of fancy over reason is a degree of insanity. — Johnson
Without grace The heart's insanity admits no cure. — Cowper
2.
(Law) Such a mental condition, as, either from the existence of delusions, or from incapacity to distinguish between right and wrong, with regard to any matter under action, does away with individual responsibility.