From Traderpedia

Definition: A trader who trades in person using the open outcry method at the exchange on their trading floor, in the designated area for his particular market called a pit.

Pit traders are also referred to as locals and will additionally be exchange members, owning or leasing a seat on the exchange.

A typical pit trader will be big, loud and wearing a brightly coloured trading jacket. They generally don't take kindly to hippies. Link to Times article

Pit traders are required to be registered with the regulatory bodies such as the National Futures Association.