sitting on a powder keg
In imminent danger, in an explosive situation, as in Our office is sitting on a powder keg while management decides whether or not to close us down. This metaphoric term alludes to sitting on a keg of gunpowder that could go off at any moment. [First half of 1900s]
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.