The 'Gom Jabbar' test, in "Dune," is a critical test of human consciousness and pain endurance conducted by the Bene Gesserit. It involves placing one's hand in a box that simulates intense pain, with a poisoned needle (the Gom Jabbar) held at the subject's neck. The test measures the subject's ability to overcome primal instincts and endure pain, a sign of advanced consciousness and control.