Our own definition: homobiota = life like us.

We can distinguish two possible meanings:

* life that's on Earth

* life that's directly related to us or otherwise indistinguishable from life related to us (eg: same biochemistry)

We mean the second one of these, because we don't know whether life that's on Earth is special in any way - currently it looks like everything in the first category is also in the second category but that might turn out to be wrong. (There might be unrelated life in what's called a "shadow biosphere".)