From Traderpedia

An individual pro trader who trades for his own account, historically on an exchange trading floor but the term local is now more applicable to the traders at an Arcade, and whose activities provide market liquidity. See also Floor trader.

With the rapid expansion of electronic trading and the demise of open outcry as many exchanges close their trading floors, many former pit traders formed their own trading firms as they made the transition to the screen trading. These trading firms came to be known as arcades, and since the majority of traders were former pit traders the definition of a local came to include pro screen traders.