Ogyaru is an archaic term for a Gyaru (gal) that is dirty, that doesn’t shower or change their clothes. Some even say they sleep on the streets. It is a term that holds it roots in the beginnings of Gyaru when it started as a rebellious style as it was very against the norm to not wash or change your clothes, particularly in japanese culture where it is common to bathe every day. Though that is not where it mainly stems from. Alot of gyarus come from trouble homes and become runaways living on the street. So they weren't always able to take baths and have clean clothes yet they still tried to keep themselves looking pretty and put together despite the odds.
This term is not often used in regards to contemporary Gyaru due to the evolution of the style.