(From "rip off" - to steal) To copy audio or video, typically from a compact disc or DVD, to a file on a computer hard disk. A dedicated program to do this is called a "ripper" though it is often a function of player software.
Ripping usually includes converting the data to a format that is more suitable for computer playback, e.g. MP3 digital audio or DivX video. The process is entirely digital so it is possible to make a perfect copy of the data. However the resulting files are large (a few megabytes for an audio track, a few gigabytes for a film) so the conversion often includes compression to reduce the file size at the cost of some loss of quality.
While it may be legal to do this for personal use, distributing a ripped copyright work to others could result in prosecution.
See also ripcording.