Is it Flirtation? or is it Sexual Harassment?
Mutuality is the key that distinguishes flirting and sexual harassment. If there is not equal participation and initiation by both people, then the behavior is unwanted. Note: if the feelings are mutual...don't do this at work. It is highly unprofessional.
Examples of Sexual Harassment
Verbal
Language that degrades such as "girl", "sweetheart", "hunk", "doll", or "honey".Turning work discussions to sexual topics, telling sexual jokes or stories. Making sexual comments about someone's clothes, anatomy or looks.Repeatedly asking a person out who is not interested.Discussing or spreading rumors about a person's personal sex life.Inquiring about a person's social or sexual life.Turning conversations into sexual innuendo.
Non-Verbal
Displaying visuals which are sexually suggestive.
Staring at someone, or looking a person up and down.
Following a person, or frequenting their work area.
Giving personal gifts.
Gestures, winks, etc.
Physical
Massage around the neck or shoulders.
Touching a person's clothing, hair or body.
Standing close or blocking a person's path.
Brushing up against a person.
Hugging, kissing or other expressions of affection.
Touching oneself in a sexually suggestive way.
Information from the Center for Human Rights, Washington State University, USA
REMEMBER: If the behavior makes you uncomfortable, you have the right to say NO and tell them to stop.