Member Firm

What Does Member Firm Mean?
A broker-dealer in which at least one of the principal officers is a member of either the New York Stock Exchange (NYSE), another major stock exchange, a self-regulatory organization or a clearing house corporation.

Also referred to as "clearing member".

Investopedia explains Member Firm
One seat (membership) on the NYSE usually costs more than $1 million. Owning a seat allows on the NYSE allows a person to trad on the floor of the exchange, either as an agent for someone else for for his or her personal account.