The term 'chatter endlessly' can be described by the crossword solutions of 'PRATE' (5 letters), 'GAB' (3 letters) and 'runon' (5 letters). PRATE is an informal verb meaning to talk in a foolish or aimless way, often for a long time. GAB is another informal verb meaning to talk rapidly and at length, especially about trivial matters. Runon is an adjective meaning continuing without pause or interruption. All three words describe talking for a long period of time, often about trivial matters, without pause or interruption.