The omniverse is the unfathomable everything inside, as well as outside existence from all the atoms to beyond the edge of space, all dimensions/alternate realities and the sum of all the verses combined (the microverse, universe, multiverse, megaverse, metaverse, etc.).
(Note: The omniverse isn't to be confused with the universe. Please see my definition of the universe for more information).
In the Ben 10 franchise It means:
1. The whole Ben 10verse, including all universes, dimensions etc..., that composed his absolute entirety
2. The 4th instalment cartoon series of the classic continuity
3. A cancelled mmorpg videogame of the franchise that wasn't based on the 4th series only sharing the same name
4. A trademark that Cartoon Network registrered in order to use It for Ben 10 products most likely because they share the prefix also with the iconic watch-like device use by the protagonist plus etymologically means ''allverse''
Grandpa Max warned the outer-dimensional Tennyson trio ''That alien X threatens the entire omniverse''
Every choice, every memory, every Indivuniverse you’ve ever lived sits inside the Omniverse — the total field where all potential and all experience coexist.
The unfathomable everything beyond the omniverse (all things inside & outside existence) and the edge of all space.
'If you travel beyond the edge of all space and everything in existence, you might arrive at the extra-omniverse: the unfathomable thing, outside of all that is.'
A cesspool of vile, wretched beings. It is a semi-fictional hub of perversion and idiocy, where one's safety is constantly endangered.
'Abandon hope all ye who enter here' is a commonly used quote in regards to Shiro's Gaming Omniverse.
'Never trust Sabr, Void and Reform' is an unspoken rule made for one's survival.
'Praise be Jux, the Mother, for The Opportunity' is a common chant among the local cult zealots.