It means: “Three Dimensional Object”

Digital three-dimensional objects are abbreviated like “3DO”. But this can also refer to the mysterious company that manufactured the 3DO Interactive Multiplayer consoles.

We live in a Three Dimensions reality. The objects around you, the ones you can pick up, touch, move around and destroy, are three-dimensional. These shapes have 3 dimensions: Up and Down (height), Left and Right (width), and a third dimension: depth. Cubes, prisms, pyramids, spheres, cones, and cylinders are all examples of three-dimensional objects. Three-dimensional objects can be rotated in space.

In physics, geometry and mathematical analysis, an object or entity is three-dimensional if it has three dimensions. That is, each of its points can be located by specifying three numbers within a certain range. Example: width, height and depth.

The space around us is three-dimensional to the naked eye but, in reality, there are more dimensions, so it can also be considered a four-dimensional space if we include time as a fourth dimension. The original human Kaluza-Klein theory postulated a five-dimensional spacetime; String theory takes up that idea and postulates according to different versions that physical space could have 9 or 10 dimensions.

Anyway, without going any further, in this case we are talking about digital three-dimensional objects, 3D designs that can be printed or imported into the theoretical digital world of Video Games. And of course, the format in which toys are translated by using a portal to digital worlds, where everything they are is transformed into digital information that can be translated and dumped into digital worlds, and then return with this same information to the physical reality.

This 3DO normally refers to digital files that can be 3D printed, which are nothing more than a set of coordinates of points and lines that form the geometry that compose them. But no more than that, a geometry, without any other attribute.

Sources for this article:

https://amnh.org/explore/ology/physics/thinking-in-three-dimensions2