Definition: A letter bomb is a type of explosive device that is hidden inside an envelope or package. When someone opens it, the bomb explodes. In this context, it is a noun.
In more advanced discussions, "letter bomb" can be used metaphorically to describe any unexpected and harmful surprise, particularly in communication. - Example: "The unexpected news was a letter bomb that shocked the entire team."
In a broader sense, "letter bomb" can also refer to any piece of correspondence that contains harmful or shocking information, but this is more of a figurative use.
While "letter bomb" itself is quite specific and doesn't have widely recognized idioms or phrasal verbs associated with it, you might encounter phrases like "drop a bombshell," which means to reveal surprising or shocking information.
Remember that the term "letter bomb" is serious and often associated with criminal activities.