Intercontinental ballistic missile

 is the abbreviation for "InterContinental Ballistic Missile". An ICBM is a ballistic missile with a long range typically designed for nuclear weapons delivery (delivering one or more nuclear warheads).

Fallout 3
ICBM silos can be found throughout the Capital Wasteland. A (non-functional) ICBM launch terminal, launch codes, and facility can be found at Fort Constantine. The launch codes are for a Minuteman XI missile.

Fallout New Vegas
Raul Tejada recalls seeing Mr. House's anti-missle defense systems shoot down Chinese ICBM's during his unmarked quest Old School Ghoul. ICBMs can also be seen throughout the Divide, stationary and while in flight before detonating, and their warheads can also be seen and detonated.