Giving a guy Viagra won't always give him an erection you know. I think might want to reconsider your wording, also. Sexual assault might be a better way to express it. So if a woman ties a guy down, pulls down his pants, sucks him without his permission (and he does not get hard) is he 'raped.'... I would say yes. But as I said, sexual assault is the better term, IMO. If same woman put a butt plug up his ass without permission, is it rape. Again, yes....so yes.. a guy can be raped. You (OP) sound like you are considering rape as a guys penis in a womans vagina only. Remember, rape is a crime of violence, not sex.