In AI speak it would sound like this: "remove your mobile hardware from this player's SOI". I ended up wiping out the Altarians but it was not easy. I had to go to war much earlier than was comfortable. Our military tech was too close. I actually lost some fleets, but I admit it was more fun this way. I'll never play another game on anything less than Tough.
One interesting observation in this game (not sure if this was a quirk in this game only): None of the other Civs researched mass drivers or armor. Each and every one of them went full bore into missiles and point defense. Some gave a minor nod to beam/shields. Once I noticed that, my ships started cutting through them like warm butter. And they never caught on with armor research. None of them.
Another note: The Drengin kick ass! I set them up as a proxy to distract my 3 biggest rivals, fully expecting the Drengin to get slaughtered, but lo and behold they held on, battle after battle. They were in the center of the map with only about 7 planets, fending off invasion armadas from every direction. I was so impressed I made them an ally and will share the galaxy with them.