Froter
Froter is individual with mental disorder correlated to sexual misbehavior. Individual with this mental illness satisfies him/herself with rubbing body parts or whole body against other people, clothed or not. This deviation is harder to recognize in the public as other sexual anomalies mainly because its "soft nature" for example its mostly performed in public transportation, shops, airports etc. where crowds of people are usually located. This is also the reason why this sexual behavior anomaly is not as publicly known as many others. For the first time this sexual misconduct was mentioned in published study of Doc. Thomas G. Gutheil M.D. from Department of Psychiatry, Harvard Medical School in Boston in his book Ethical Issues in Sexual Misconduct.
Observe your surroundings ;) during times when you are in public places where lots of people gather you might spot one of them Froters