radar; Sometimes, intrepid O-girls decide to wear skirts made of fabrics other than denim. Since these broads don't have any other distinguishing features - such as the yarmulkes worn by their male counterparts - this may confound those who are unable to pick up orthodox vibes.
Yitzhak: Is that chick an o-girl or is she just wearing a skirt because formal attire is required?
Moishe: Dude, that "chick" is Rebbetzin Goldberg!
Yitzhak: Oy, my O-dar is pitiful.
Moishe: Yeah, tell me about it.