The term 'symbol on many a bumper sticker' is often represented by the five-letter word 'HEART'. The HEART symbol is a popular choice for bumper stickers, as it conveys a message of love and acceptance. It is also used to express support for various causes, such as environmentalism, animal rights, and social justice. The HEART symbol has become a universal sign of kindness and compassion, and its presence on a bumper sticker can be a powerful statement.