Having found the antimatter minefield out beyond Star One, Avon surmised that "the intergalactic drive" may have been developed. His use of the term suggests such a drive was a much-mooted, theoretically possible but as yet undeveloped technology. The Federation certainly seemed to be working on such a project, designing a drive using monopasium 239 to be fitted to the "hyperspace ships" mentioned by Ro in Horizon.
See also PHOTONIC DRIVE, SPEED, TIME DISTORT, HYPERDRIVE.