A Boom Tube is a slang expression for an extra dimensional point-to-point travel portal opened by a Mother Box used primarily by the New Gods of New Genesis and Apokolips. The moniker derives from the loud "BOOM" that erupts when a tube is created.
Orion once said that a boom tube "stems from the waves of the mind" but they allow people to travel interstellar distances almost instantaneously by creating a wormhole through space. The tubes need to be generated or opened by another device, commonly a Mother Box. Boom tubes are powered by the mysterious element X, which serves as a matter threshold.