бомба?!
пример/источник?

What it is the meaning of slow boil? Ex. "He's such a slow boil"
"Slow boil" can literally mean "a boil that was achieved slowly," as in cooking soup or something. Many recipes call for a "slow boil," meaning that you cook with a weak flame or a low temperature.
As an idiomatic expression, "slow boil" can mean getting angry slowly.
In your example, that wouldn't make sense. "He's such a slow boil" sounds as though it means "It takes him a really long time to get excited" or "It takes him a really long time to get started on something."