The definition of whom is "a highly skilled professional going abroad in order to perform a contract or permanent work" or something to that mater...
In its broadest sense, an expatriate is any person living in a different country from where he or she is a citizen. In common usage, the term is often used in the context of professionals sent abroad by their companies, as opposed to locally hired staff (who can also be foreigners). The differentiation found in common usage usually comes down to socio-economic factors, so skilled professionals working in another country are described as expatriates, whereas a manual labourer who has moved to another country to earn more money might be labelled an 'immigrant'. There is no set definition and usage does vary depending on context and individual preferences and prejudices.
The term 'expatriate' in some countries also has a legal context used for tax purposes. An expatriate living in a country can receive a favorable tax treatment. In this context a person can only be an expatriate if they move to a country other than their own to work with the intent of returning to their home country within a period of no more than 5 fiscal years. This number of years can vary per tax jurisdiction, but 5 years is the most commonly used maximum period.
came to Poland 8 years ago with the intention of staying here. What does that make me?
Based on your description, you are an ' immigrant '