Well, if we're trying to define "pagan" as it is used in modern English and other western languages, then Zoroastrian would probably fit.

"Pagan" has a pretty odd history. It's derrived from Latin words used to describe rural peasants and the land they lived on. The Latin word paganus was a near synonym to "rustic," but it was reinterpreted after the Roman Empire officially adopted Christianity because polytheistic religions persisted in rural areas even after the cities were majority Christian. By the medieval period, there was a general understanding in Christian Europe that a "pagan," was someone who did not worship the Christian God - not necessarily that they were not Christian but that they didn't profess to worship the same God as Christians.

As a result, Jews were generally considered non-pagans and how Christians discussed Islam changed as Christian scholars gained a better understanding of the Muslim faith. Early Christian responses to Islam, like those of Isidore of Seville, were quick to characterize Muslims as pagans, but after a few centuries of regular contact that was less common. By the Late Middle Ages, most educated Christians knew that Islam claimed the same God as Christianity and use of "pagan" was mostly limited to intentionally derogatory polemics.

By this definition, Zoroastrianism has to be pagan because Zoroastrians do not believe that Ahura Mazda is another name for the Abrahamic God.

There is a much more modern trend that can complicate this definition. "Neopaganism" or "Contemporary paganism" is the practice of reviving the religious beliefs, gods, and practices of pre-Christian and pre-Islamic cultures. Sometimes this is extended to include things like Mari Paganism in the Volga River basin, which has been practiced continuously, but generally excludes the likes of Zoroastrianism, Hinduism, and non-European indigenous religions. For people who actively identify themselves as "Pagans" in the west today, Zoroastrianism isn't included.

But you said you're from Iran, so we should probably also look at the Islamic context. Obviously, "pagan" is not a word from any "Islamic" tradition. The Arabic religious terms usually translated as "pagan" are usually musrikun (idolater or polytheist) and kafir (non-believer). Neither of these terms has a simple definition either. I have to admit, I can't find much written on use of musrikun to describe Zoroastrians. I think by most logical definitions it would have to apply, but there are some modern Zoroastrians who would argue that they are at least as monotheist as Christians.

Kafir is at least better documented in regard to Zoroastrianism. Generally the People of the Book are not treated as kafir in historical Islamic thought (though even that isn't universal). Under the medieval Muslim dynasties (both of the Caliphs and independent kingdoms in Iran) Zoroastrian legal status shifted back and forth between dhimmi (resident People of the Book) and Kafir.

After the initial conquest of Iran, when Zoroastrians were persecuted as part of the process of conquering their lands, the early Caliphs granted them dhimmi status. The Quranic basis for this is up for debate. Zoroastrians are mentioned without being explicitly condemned in the Quran, but they are not included in the list of People of the Book (Jews, Christians, and Sabaeans). However, on a purely practical level, the Rashidun and Umayyad Caliphs simply couldn't persecute the entire population of the Sassanid Empire as pagans. This same scenario played out in India when the Umayyad Caliphate began interacting more extensively with Hindus.

Under the Abbasids, after Islam had spread through Iran, Zoroastrians lost their legal status as dhimmi and were labeled kafir. Their temples were destroyed. They lost the right to their own religious courts. Zoroastrian practices and scripture were targeted. This is also the period when the Persian language was officially suppressed for the first time. Of course, the Abbasid period was long and there were periods on increased and decreased persecution.

Since then, the legal status of Zoroastrians has fluctuated between kafir and dhimmi under different Muslim rulers, and various Islamic scholars have offered different interpretations both in and beyond Iran.