Since my summer is filled with catch up reading and writing, I have become very aware that post-colonial hybridity has found fertile ground in recent publications in the field of early Jewish and Christian studies. In postcolonial studies, "hybridity" refers to "the creation of new transcultural forms within the contact zone produced by colonisation" (Aschroft, Grittiths, Tiffin: Post-Colonial Studies, p. 118)
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?!