Definitions for "Microkernel"
A kernel design in which a very small kernel component implements scheduling and IPC, and other "servers" which run as processes implement most of the kernel's behavior, communicating between each other via message passing.
a highly modular collection of powerful OS-neutral abstractions, upon which can be built operating system servers
a highly Spartan modular subsystem composed of OS-neutral abstractions, providing only essential services such as people
a component-based structure which improves portability at the expense of performance