Lead balloons are a metaphor for a failed endeavor or project. They are often used to describe an idea or plan that was doomed from the start. The term 'lead balloons' can be broken down into two crossword solutions: BOMBS (5 letters) and DUDS (4 letters). Bombs are explosive devices that cause destruction, while DUDS are items that fail to work as intended. Together, these two words paint a picture of a failed endeavor that was doomed from the start.