Would you consider my grandfather an oligarch?

My grandfather was very wealthy during the communist era of our country (Romania). Extremely intertwined with the PCR (Romanian Communist Party) and Securitate (secret police). He'd travel abroad recreationally - for business purposes, sent his kids to study abroad in the UK, had imported luxury goods, etc. After the end of communism (1989), he became even wealthier. He basically bought a lot of dirt cheap land / property in what would later become the most expensive / trendiest areas of Bucharest and developed it + led the privatization of the Port of Constanța (shipping / port operator). Is the term oligarch reserved for post-Soviet states? What does oligarch really mean?