It depends upon how sexual harassment is defined in your country. Where do you live? If you are in the US, here is how it is described by the Equal Employment Opportunity Commission:
It is unlawful to harass a person (an applicant or employee) because of that person’s sex. Harassment can include “sexual harassment” or unwelcome sexual advances, requests for sexual favors, and other verbal or physical harassment of a sexual nature.
Harassment does not have to be of a sexual nature, however, and can include offensive remarks about a person’s sex. For example, it is illegal to harass a woman by making offensive comments about women in general.
Both victim and the harasser can be either a woman or a man, and the victim and harasser can be the same sex.
Although the law doesn’t prohibit simple teasing, offhand comments, or isolated incidents that are not very serious, harassment is illegal when it is so frequent or severe that it creates a hostile or offensive work environment or when it results in an adverse employment decision (such as the victim being fired or demoted).
The harasser can be the victim’s supervisor, a supervisor in another area, a co-worker, or someone who is not an employee of the employer, such as a client or customer. Source
While what your boss did would make me feel uncomfortable as well. If we go by the above guidelines, it sounds like calling an employee beautiful and sexy wouldn’t be much of a case. From the harassment training we were all required to attend each year at work, which had educated human resources and legal teams, the best thing to do in your situation is to confront the person, boss or not, about what they said. It would help if you had a witness present. People, even bosses, make mistakes.
If you allow him the chance to apologize for his behavior, it sets the scene for the repercussions if it happens again. If he denies it, simply state that it felt like sexual harassment, and that should stop him from ever doing it again. In the future, do not enter enter his office and allow him to close the door. If you respect this guy on any level, give him a second chance. If not, it’s time to start looking for another job for more reasons than the feeling of being sexually harassed.