Definition of "uncharted"

Far out in the uncharted backwaters of the unfashionable end of the Western Spiral arm of the Galaxy lies a small unregarded yellow sun.

1979, Douglas Adams, The Hitchhiker's Guide to the Galaxy

John Wesley Powell ... the one-armed Civil War veteran led nine men in four wooden dories down the untamed and uncharted Colorado River and into the equally untamed and uncharted Grand Canyon.

2013 November 27, John Grotzinger, “The world of Mars ”, in The New York Times‎