What bookdealers really mean. A dictionary by Tom Congalton and Dan Gregory (Between the Covers), with additions from other sources
A manuscript or letter that was created using carbon paper, i.e. the second (or later) copy in the typewriter, a device used by hard-drinking authors before the invention of the personal computer (if you need a ribbon for one, good luck). Carbon copies of manuscripts can be collectible if they exhibit hand corrections.