The term that best describes Iggy Azalea's behavior in adopting Black slang, vocal patterns, and mannerisms in her music is cultural appropriation.
What is Cultural appropriation?
Cultural appropriation is when a dominant culture or group adopts, in an exploitative, insulting, or stereotyped manner, specific language, behaviors, attire, or traditions from a minority culture or social group.
The term "cultural appropriation" describes the taking of components or features of another culture without acknowledging or appreciating its importance. In this instance, white Australian artist Iggy Azalea is incorporating elements of Black culture into her songs.