The only term I've ever heard is "multiverse" which includes all universes. But if you mean just a single universe, I don't think there is. If its a universe for a specific canon most people just say "(Canon) universe."
If you're talking about fictionkin specifically, I've heard "canon" and "timeline" used pretty much interchangeably. The only difference I've seen is that a "canon" is typically used to describe kin that matches the source material closely, whereas a "timeline" can divert from the source material more.
"Canon" has always been a fictionkin-exclusive term in my experience, as otherkin and therians have no source material, but "timeline" can be used by any kintypes. It's just most commonly used by fictionkin.