Meyer Wolfsheim is Jay Gatsby's shady business partner. Nick meets him for the first time in chapter four, when he travels into the city with Gatsby. Meyer Wolfsheim is a successful bootlegger and gambler, and he notoriously fixed the 1919 World Series. Nick's introduction to Meyer Wolfsheim in chapter four is the first piece of hard evidence that suggests that Gatsby is involved in illegal activities. Meyer also speaks about his friend, Rosy Rosenthal, who was shot to death outside of the restaurant across the street, which is a red flag that implies that he is involved in the criminal underworld. After Gatsby dies, Meyer tells Nick that he (Wolfsheim) raised Gatsby up from nothing and is solely responsible for his success in the bootlegging business. Despite being close friends and business partners with Jay Gatsby, Meyer Wolfsheim does not attend his funeral and distances himself from the entire situation after learning about Gatsby's death.
Meyer Wolfsheim, Gatsby's friend and business acquaintance, is one of The Great Gatsby's most mysterious characters. A gambler and bootlegger who appears to be involved in organized crime, Wolfsheim's main claim to fame is that he fixed the 1919 World Series. Nick is shocked by this information and its implications for followers of the game: "It never occurred to me that one man could start to play with the faith of fifty million people—with the single-mindedness of a burglar blowing a safe," Nick reflects in chapter four of the novel.
Wolfsheim is significant to The Great Gatsby in that despite his claims of Gatsby's moral decency and intellectualism, Wolfsheim's very association with him casts doubt on Gatsby as a person and deepens the mystery about his origins. It becomes apparent to readers that if Wolfsheim fixed the World Series, Gatsby may have acquired his fortune through illegal means and is likely involved in questionable activities. Try reviewing chapter four, where Wolfsheim makes his entrance into the story and noting what other details illustrate his character and demonstrate his role in the novel.