A hybrid, if I remember my biology correctly, is an often (always?) sterile offspring of two different taxa. So a donkey and a horse make a mule. A blackberry and a raspberry make a loganberry. A fallen angel and a human woman make a giant (okay, not in our biological world, but in biblical mythology!).
I have nothing particularly against the term "hyridity" when it is applied in the context of two or more different aspects of society-culture morphing into something other, although I know that the word is debated in post-colonial circles.
In religious studies, one of the words that we used to use to talk about this phenomenon was "syncretism," which still seems like a good descriptor to me. So the worship of Serapis was a religious movement that morphed out of the mixture of Egyptian devotion to Osiris and the religious sentiments of the Greek colonizers. His name is a combination of Osiris and Apis, a bull god that was worshiped at Memphis. The Greek ruler of Egypt, Ptolemy I established the cult of Serapis at Alexandria and incorporated features of Greek worship including iconographical features of Zeus.
As a side - when I was in Egypt last, I made the trek down to Alexandria - a spectacular city on the coast - and visited the Serapion site. This picture is from that adventure. It was an incredibly beautiful day. Below the Temple ruins was a huge underground library, with shelves carved out of the rock ledges.
Although "hybridity" might be used to replace our term "syncretism", I wonder if its application as a descriptor of early Judaism-Christianity is really such a good idea. To apply this term to Judaism-Christianity before Judaism and Christianity became distinct, only serves to confuse an already confusing nomenclature. Christianity was Jewish for almost two centuries, although by the mid-second century some demarcations are beginning to be either created and/or acknowledged. But this entity was not a hybrid that developed out of Judaism and Christianity merging! It was more like an androgynous entity which became two religious traditions over a long period of time. Maybe I should coin the term "androgynity" to refer to this phenomenon?!