The term 'counterpart of DOWN' has a crossword solution of 'ACROSS', which is a six-letter word. The term 'ACROSS' is used to describe a direction that is perpendicular to the direction of 'DOWN'. It is often used in reference to movement, such as when someone moves ACROSS a room or street. In addition, it can also be used to describe a position that is opposite to something else, such as when two people are sitting ACROSS from each other at a table.