This word is used in its proper sense in Deuteronomy 28:34, John 10:20, 1 Corinthians 14:23. It also denotes a reckless state of mind arising from various causes, as over-study (Ecclesiastes 1:17; 2:12), blind rage (Luke 6:11), or a depraved temper (Ecclesiastes 7:25; 9:3; 2 Peter 2:16). David feigned madness (1 Samuel 21:13) at Gath because he "was sore afraid of Achish."

Noah Webster's New International Dictionary of the English Language

1. (n.) The condition of being mad; insanity; lunacy.

2. (a.) Frenzy; ungovernable rage; extreme folly.