Cruise missile is a generic term for self-propelled guided weapons which fly like normal aircraft for much of their flight.
In military terms, they are cheap (approximately $600,000), simple to build and can be launched in large numbers from sea, land and air.
The simplest cruise missiles (developed by the Chinese) have a range of approximately 100km (60 miles).
But the US arsenal includes weapons that can be fired at targets from up to 3,000km away yet hit a target with a claimed accuracy of a few metres.
Use this guide to find out how a cruise missile works.