ewwy means: If you spot a hot girlguy from the behind and start walking towards her hehimr then she stops and turns and this person is too ugly for you so turn around and go the opposite direction. (in Community Dictionary, added by Eugenio Ramírez)
What else does ewwy mean?
- You stop a brotherly man from trying to have sex. (in Community Dictionary, added by Esther Delgado)