The term 'What 'X' May Mark' can be answered by two crossword solutions: SPOT (4 letters) and BURIEDTREASURE (14 letters). SPOT could refer to a physical location, such as a landmark or a point of interest. It could also refer to a figurative SPOT, such as a position in a competition or a place in a line. BURIEDTREASURE is a phrase that is often used to describe something valuable that is hidden or concealed. This could refer to a literal treasure, such as a chest of gold coins, or it could refer to something more abstract, such as a secret talent or a hidden opportunity.