The Grecian Jews are Greek speaking Jews, Jews who grew up outside of Judea. They met together in their own synagogue (see Acts 6:8–10). It is very likely that Saul knew them all well since he came from Cilicia, was Greek speaking and present for Stephen’s trial and stoning (see Acts 7:58–8:1).1
29 And he spoke and disputed against the Hellenists. But they were seeking to kill him.