Verbal abuse and offensive gestures can be upsetting and cause a person distress. Generally although not acceptable behaviour, if this is a one-off incident the complainant may decide to let it pass, or speak to the person who has verbally abused them themselves.
If the abuse is not a one-off incident and is happening on a regular basis, this may amount to harassment. This all depends on how the abuse affects the complainant and how it makes them feel. If it is causing a person to feel upset, fearful as to what may happen, or is generally affecting their quality of life, then this amounts to harassment.
Complainants should contact their local police for advice.