Your browser does not seem to support JavaScript. As a result, your viewing experience will be diminished, and you have been placed in read-only mode.
Please download a browser that supports JavaScript, or enable it if it's disabled (i.e. NoScript).
a small spacecraft, with no one travelling in it, sent into space to make measurements and send back information to scientists on earth
Share your knowledge with the community
Browse our collection of 300,000+ community-written definitions
