Microcode - machine code which executes on a state machine internal to a processor or on a simple state machine device that is independent of the main execution pipeline - e.g. the Bt878 RISC processor executes code fetched from the x86 processorís memory over the PCI bus - this code is microcode from the viewpoint of the x86 system.
Microparallelism - parallel processing inside the CPU core.
MMU - Memory Management Unit, a block in most CPU cores which provides virtual to physical address mapping, address range checking, and can protect read-only address ranges from unintentional update.
Module Loading - when an ELF module is transferred to an embedded target and dynamically linked into the kernel and other application code on the fly.
MTD - Mapping to Device, a term used to describe Bottom Half code used in a flash file system driver.