An ICBM is a missile — a weapon that flies a very long way by itself, with no person inside. The letters stand for intercontinental ballistic missile. “Intercontinental” means it can travel from one continent to another, thousands of kilometres. “Ballistic” means that after the engines push it up, it mostly follows a high curve through the sky and then comes down, like a thrown stone, only vastly farther and faster. Countries keep ICBMs as a military threat. You will hear the word in news, history, and talk about war, not at the dinner table. People say the letters: “I-C-B-M.” It is a cold, technical word. Though actually, in casual speech some people just say “long-range missile” and mean roughly the same idea; ICBM is the precise name for this very long-distance type.