The hybrid DNA hypothesis refers to the theory that proposes a possible hybridization event between Neanderthals and modern humans. However, there are several other synonyms to describe the same phenomenon. Some of the common alternatives include the hybridization hypothesis, interbreeding hypothesis, admixture hypothesis, and hybridization model. These terms are often used interchangeably and refer to the mixing of genetic material between two different species or sub-species. They are also used in other settings such as plant and animal breeding. Overall, the hybrid DNA hypothesis provides a possible explanation for the presence of Neanderthal DNA in modern humans.