Is it permissible to use the word "Islamic" instead of "Muslim" to describe a person?

Allah named the Ummah of response [to His call] as "Muslims," as He Almighty said: "He [Allah] named you Muslims before and in this [Qur'an]." So the word "Muslim" is the original [term], whereas "Islamic" is a term applied to those who work for Islam and strive to support and revive it from among the general Muslims. There is no harm in using this term as long as it is a [conventional] designation, especially since those who work for Islam seek for the entire Ummah to adhere to it.