An adjective used to describe one way of getting the missile out of the missile silo; shockingly, it's the opposite of hot launched. During a cold launch, the missile doesn't ignite its booster until after it is well clear of the silo--usually the base of the missile is several meters above the lip of the silo. "But how in the hell," you might ask, "does it get there?"
How the hell it gets there
At key-turn, a pancake motor is ignited inside the silo, below the missile to be launched. Despite it being, essentially, a discus of solid rocket fuel, it doesn't burn hot--it's formulated to burn very fast, instead: for all intents and purposes, to sublimate explosively. The missile sits on top of this cloud of rapidly expanding gas. Depending on the design, the missile is either sitting on a little stool called a "sabot" or it's wrapped in Teflon-coated foam pads the size of sofa cushions that serve to turn the missile into a piston. The expanding gas exerts tons of force over a very short time, and the missile pops out of the silo or launch canister like the cork out of a champagne bottle. The sabot or cushions fly out of the silo, too and will usually be visible in launch photos, looking like a small UFO or confetti, respectively.
"...Explode into space!"
The rapid acceleration in the vertical direction arms the first stage, but doesn't fire it. The on-board accelerometers and gyroscopes don't fire the first stage until the missile is well clear of the silo. From a distance, you see smoke spurt from the mouth of the silo, the missile knifes up through it, and for a magic moment, it seems to hang in the air for seconds on end... then you blink and squint from finally seeing the flash of the booster's ignition.
Freshman Engineering Major or other astute Emperor's New Clothes type: "But what happens if the booster, y'know... doesn't ignite?"
Jurph: "The missile or rocket falls back down onto the silo, and if it's a liquid-fuel rocket, its hypergolic fuels almost certainly combine en masse. Duck. If it's a solid-fuel rocket, your odds are a little better, but, well... duck. The pancake motor isn't hot enough to ignite the booster inside the silo, but if tons of solid fuel come cascading down onto it, all bets are off."
Cold Launched Systems
The Peacekeeper is the only American missile that is cold launched (not counting SLBMs, which are all essentially cold launched), and it launches from a silo. The Russians, however, have several systems that cold launch--some from silos (SS-18), some from TELs (SS-25), and some from trains (SS-24). Many of these also have spacelift variants; despite the consequences of a launch failure, the willingness of customers to place a multi-million dollar satellite on the tip of a cold launched system is a testament to the method's reliability.