The term 'let alone' is a phrase used to emphasize that something is even more unlikely or impossible than what has already been mentioned. The two crossword solutions for this phrase are 'NEGLECT' and 'leavebe'. NEGLECT means to fail to take proper care of something, while leavebe means to leave something alone or untouched. Both of these words can be used to emphasize the idea of not doing something, which is the same concept as 'let alone'.