Opposite of typical. Typical is considered customary. They way things have always been done. Typical is the way people expect things to be. Atypical is not the way that most people expect things to be as in not the custom that people are used to.
If you saw this in reference to the Lesbian Group, then "I believe" it is saying that it isn't what people have come to expect lesbians to be about. Many people have a preconceived idea that lesbians hate men, like to wear men's clothing and have very short butch-style haircuts. That isn't necessarily true. I have many lesbian friends who like men (they just love women), they are very girlie and some have long hair. Maybe if you look at the name of the member who created the group, you can ask them more questions about the group.
opposite of normal .