What is Insane?

Legal Definition
One deprived of the use of reason, after he has arrived at the age when he ought to have it, either by a natural defect or by accident. Domat, Lois Civ. Lib. prel. tit. 2, s. 1, n. ll.
-- Bouviers Law Dictionary
Legal Definition
Unsound in mind; of unsound mind; deranged, disordered or diseased in mind. Violently deranged; mad.
-- Black's Law Dictionary
Legal Definition
Mentally unsound; mad; deranged. See 13 Mich. 427, 87 Am. Dec. 774.
-- Ballentine's Law Dictionary