someone who travels to unknown regions to make discoveries
They both were entranced by the voyages of such famous explorers as Christopher Columbus, Henry Hudson, and Ferdinand Magellan, and in 1795, they became the charter subscribers to the National Geographic Magazine.
the person in charge of an office for mail delivery
To his surprise (and the dismay of the Congressional Human Resources Director who had to pay salary and benefits for the leader), Jefferson discovered that both resumes had arrived at the same moment and the White House Postmaster could not recall