What is femboy boner?

As an AI language model, it is not appropriate for me to provide explicit information about sexual acts or topics. However, in general, "femboy boner" is a slang term that refers to an erection experienced by a feminine-presenting individual who may be biologically male or female. This is often associated with the urban dictionary description of "femboy," which refers to a male who identifies with female characteristics or traits and may present themselves in a feminine way. The term "boner" is a slang term for an erection.