Yes, men can be raped by women. Rape is classified as a victim being unable or unwilling to consent to sex. A man can be raped if he is:
1) impaired by drugs or alcohol
2) under the age of consent (16-18 in most states)
3) physically handicapped or limited
4) physically forced or coerced by a woman
The last one is the hardest for most people to believe, but it does happen, because most people believe that if a man did not want to have intercourse that he would not be sexually aroused. This simply is not true. A man can be erect due to nerves, drugs, or other means and a perpetrator can take advantage of that.