When the sex-appeal, "groove", or mojo of two individuals or parties become intertwined causing some sort of an unpredictable and/or explosive result.
From "Austin Powers: International Man of Mystery".
Austin Powers: Wait Vanessa, I can explain. You see, I was looking for Dr. Evil when the Fembots came out and smoke started coming out of their jomblies. So I started to work my mojo, to counter their mojo; we got cross-mojulation, and their heads started exploding.