A device that treats data I/O as a continuous stream, without consideration for the data's logical structure. For example, I/O for fixed disks and streaming tapes occurs in units of bytes that have no relationship to characters.
A device running in raw mode.
In computing, specifically UNIX, a raw device is accessed via a device file. For example, in many systems accessing /dev/hda1 will allow you to read/write directly onto/from the primary master hard drive. This raw device is typically used for paging and dumping.