Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
This word is used in its proper sense in Dt. 28:34, Jn. 10:20, 1 Cor. 14:23. It also denotes a reckless state of mind arising from various causes, as over-study (Eccl. 1:17, 2:12), blind rage (Lk. 6:11), or a depraved temper (Eccl. 7:25, 9:3; 2 Pet. 2:16). David feigned madness (1 Sam. 21:13) at Gath because he "was sore afraid of Achish."