Arbitrageur

What Does Arbitrageur Mean?
A type of investor who attempts to profit from price inefficiencies in the market by making simultaneous trades that offset each other and capturing risk-free profits. An arbitrageur would, for example, seek out price discrepancies between stocks listed on more than one exchange, and buy the undervalued shares on one exchange while short selling the same number of overvalued shares on another exchange, thus capturing risk-free profits as the prices on the two exchanges converge.

Investopedia explains Arbitrageur
Arbitrageurs are typically very experienced investors since arbitrage opportunities are difficult to find and require relatively fast trading. Arbitrageurs also play an important role in the operation of capital markets, as their efforts in exploiting price inefficiencies keep prices more accurate than they otherwise would be.