I sincerely believe it is “anti-gravity”. Years ago I knew a geophysicist that was doing gravity research for the Air Force. Even missles from an airplane are corrected for regional gravity effects. Things never quite worked out, and there were suspicions of a small repulsive gravity force. Although that was years ago and haven’t heard anything else regarding it, so perhaps it was a wild goose chase.
Sounds like you're describing "dark energy". But I don't think it's suppose to have much of an effect on minor scales like the solar system. It's thought to kick in at cosmic expansion (big Bang) scales.