Avorion is described as 'Procedural co-op space sandbox where players can build their own space ships out of dynamically scalable blocks. Fight epic space battles, explore, mine, trade, wage wars and build your own empire to save your galaxy from being torn apart by an unknown enemy' and is a exploration game in the games category. There are more than 10 games similar to Avorion for a variety of platforms, including Windows, Steam, Mac, Linux and Android apps. The best Avorion alternative is Space Engineers. It's not free, so if you're looking for a free alternative, you could try StarMade or Dyvox Pytheas. Other Avorion like games are Shores of Hazeron, ScrumbleShip, Empyrion and Galaxy on Fire.
SE is a building game where Avorion is a space empire building game.