The term CALLER CAB is composed of three words: HAILER (6 letters), UMP (3 letters) and REF (3 letters). HAILER is a person who hails or calls out for a cab, UMP is an abbreviation for umpire, which is an official in a sports game, and REF is an abbreviation for referee, which is also an official in a sports game. Therefore, CALLER CAB is a term used to describe someone who calls out for a cab, as well as an umpire or referee.