The term 'on and on' is used to describe something that continues without end. This can be seen in the crossword solutions for the term, which include 'ENDLESS' (7 letters), 'ENDLESSLY' (9 letters), 'EVER' (4 letters), 'atlength' (8 letters), 'RELENTLESS' (10 letters), and 'withoutend' (10 letters). All of these words imply a never-ending continuation, suggesting that the term 'on and on' is used to describe something that goes on forever.