Below the horizon is a phrase that refers to something that is not visible or cannot be seen. The term can be broken down into three crossword solutions: SETS (4 letters), SET (3 letters), and UNRISEN (7 letters). SETS is a verb meaning to put in order or arrange, while SET is a noun meaning a group of things that belong together. UNRISEN is an adjective meaning not yet risen or not yet come into view. Together, these words describe something that is not visible or has not yet come into view.