Below is our answer to the question: “What is Boundless?”
Boundless is an epic voxel sandbox where everyone (all players, on all platforms, in all physical locations) inhabits a single online universe.
Every world you visit is visible from every other. You can look up in the sky from your home planet, see another world, see another civilisation, see everything its inhabitants have constructed, then build a portal and seamlessly step from your world into another.
Craft a tool, build a home, forge a weapon, trade your wares, open a portal, explore a world, grow your skills, find your friends, form a clan, found a city, claim a world, conquer a Titan, birth a civilisation - make your mark in Boundless - the epic player-driven sandbox MMO.
This attempts to answer the question without using too many genre defining terms.
What is your answer to the questions: “What is Boundless?” Do you have a better answer?