

It means the murder of a woman motivated by misogyny. It is a subset of homicide and also a subset of hate crimes. It can be thought of as recognizing misogyny as a motive of hate and thus an aggravating circumstance to a homicide, and women as a protected class. Killing a trans woman or a trans man could very well get a “transphobia” label for a double hate crime, depending on the motives that get established. This is not as complicated as you seem to believe.
The word just existed since 1652