Pile on is a phrase that is used to describe the act of adding or loading something onto an existing pile. It can be used in a literal sense, such as when one adds more items to a pile of objects, or it can be used figuratively, such as when one adds more pressure or responsibility to an already difficult situation. The crossword solutions for the term pile on are 'ADD' (3 letters) and 'LOAD' (4 letters). Both words accurately describe the action of piling on, as they both imply the act of adding or loading something onto an existing pile.