Note: This info is directly taken from the main VS Battles wiki.
A Multiverse is a hypothetical set of infinite or finite possible universes that together can comprise anything from a comparatively simple collection of parallel 4-dimensional universal space-time continuums, to our own likely 11-dimensional multiversal structure, or sometimes even higher levels of reality.
This includes the entirety of space and time within a certain continuum, as well as the physical laws and constants that describe them.
Much like the main VS wikia, we draw a great distinction between characters that can merely destroy or create simple collections of universes, and ones that can destroy or create more complex higher-dimensional structures.
A Megaverse is a collection of multiverses. Since this could mean anything from a collection of simple multiverses (which would basically just mean an undefined greater number of regular 4-dimensional universes), to a collection of 11-dimensional complex multiverses, and so onwards, we do not use this term any more.
A Hyperverse is a term that we decided to use for a reality of a higher dimensional order than our own likely 11-dimensional multiverse.
We use the term Outerverse for characters, objects, and structures that are beyond outside and concept of dimensions altogether.
The definition of Omniverse varies depending on the source. We do not use this term either.