Rainbow Bridge: A physical phenomenon seen on Zandana—and predicted for this planet—where the convergence of two bodies creates what appears as a rainbow-hued bridge. This “bridge” also serves as a conduit for beings between dimensions.
(Confessions of a Rebel Angel)
The term is also used for Antahkarana which is an inner phenomenon, "the bridge between the divine Self and the personal soul" (Theosophical Art)