The term 'lead balloon' is a metaphor for an idea or plan that fails miserably. The crossword solutions for this term are FIASCO (6 letters), FAILURE (7 letters), FLOP (4 letters) and DUD (3 letters). All of these words refer to a complete FAILURE, with 'FIASCO' referring to a situation that has been mishandled, 'FAILURE' referring to a lack of success, 'FLOP' referring to something that is unsuccessful, and 'DUD' referring to something that is ineffective or unsuccessful.