A Device driver that doesn't come with source. BinaryDriver's are often used by companies that think that giving out the source to their driver gives away too much about how their hardware works. Of course because they are compiled seperately to the kernel, they tend to be bound to specific versions of the kernel, and you have to wait for new versions of your driver to be available before you can upgrade.

All in all, Binary Drivers suck :)

In the linux world, one well-known example is NVidia?'s binary linux driver for their accelerated graphics cards. Perhaps understandably, they don't want their competitors benefitting from the very optimised graphics routines that the drivers contain, but the linux community could not help fix up the inevitable bugs found in early versions of the drivers, some of which locked up machines. Indeed, bugs relating to the closed-source drivers were so common that the linux kernel folks added a special "taint" flag that indicated a binary-only driver and refused to even look at any bugs from a tainted kernel.