Shaul, there is no single "science-based definition". That is something that exists in your mind but doesn't actually mean anything to people whose job it is to write definitions. Those people base their definitions on patterns of usage, not just the opinions of scientists. Within a technical community, there will be patterns of usage that hold for that community of speakers. I know, because that is an area that I have worked with for several decades. One thing that stands out about technical domains is that the definitions will vary widely from the ones used for the same words in other domains. For example, biologists, psychologists, and physicians will have very different ways to define gender, because they interact with different aspects of those personal categories. Everyday, ordinary usage is different, because it depends on how people interact socially with each other. Like it or not, the LGBT communities are very well-established social groups that will have an impact on patterns of linguistic usage.