The phrase "Yankee horse traders" refers to shrewd American traders who are known for their savvy business acumen. While there are no precise synonyms of this phrase, there are several words that can help describe similar qualities. "Wheeler-dealer" is a term often used to describe individuals who are skilled at negotiating and striking deals. "Hustler" is another word that conveys a similar meaning, often used to describe those who are resourceful and always on the lookout for opportunities. Additionally, "sharpie" and "slickster" both suggest an individual who is cunning and adept at turning a profit. Overall, these synonyms all point to individuals who possess the same savvy, entrepreneurial spirit that defines "Yankee horse traders".