Arrancar

An Arrancar (破面) is a Hollow that has removed its mask and has gained Shinigami -like powers. Arrancar are the result of Hollows removing their masks. However, an average Hollow removing their mask would not be a problem for the Gotei 13. To hold their own against the Gotei 13 the ones removing their masks would need to be Menos or stronger. The Generic term for an Arrancar is Shinigami-Hollow Hybrid.