Collins COBUILD Advanced Learner's English Dictionary - time bomb

also time-bomb (time bombs) 1. A time bomb is a bomb with a mechanism that causes it to explode at a particular time. N-COUNT 2. If you describe something as a time bomb, you mean that it is likely to have a serious effect on a person or situation at a later date, especially if you think it will cause a lot of damage. This proposal is a political time bomb that could cost the government the next election... N-COUNT: oft adj N