A missile is an object propelled, usually artificially, in a manner against the force of gravity. That is, an object launched laterally across the earth's surface, or directly up, is a missile, but one dropped to act in accord with gravity is not.
While the term "missile" most commonly carries the connotation of warfare and perhaps nuclear weapons, the definition compasses more benign uses as well: missile technology is the foundation of the modern NASA space program, which has led to space travel.
Any major United States Armed Forces military base with missiles and hence likely nuclear weapon capabilities make it one of the primary targets among the world's major nuclear target structures in a possible nuclear war. Based with missiles being a "first strike" nuclear war target is mostly due to missile silos, bomber bases, submarine bases, and command and control (C2) centers. The enemy must neutralize these assets immediately to prevent or minimize American nuclear or other military retaliation.