gender fluid. 1  Gender Fluid is a gender identity best described as a dynamic mix of boy and girl. A person who is Gender Fluid may always feel like a mix of the two traditional genders, but may feel more boy some days, and more girl other days. Being Gender Fluid has nothing to do with which set of genitalia one has, nor their sexual orientation. No, I'm not a boy, and I'm not a girl either. I am gender fluid.