Source : WordNet®

firmware
     n : (computer science) coded instructions that are stored
         permanently in read-only memory [syn: {microcode}]

Source : Free On-Line Dictionary of Computing

Firmware
     
        Software stored in read-only memory (ROM) or programmable ROM
        (PROM).  Easier to change than hardware but harder than
        software stored on disk.  Firmware is often responsible for
        the behaviour of a system when it is first switched on.  A
        typical example would be a "monitor" program in a
        microcomputer which loads the full operating system from disk
        or from a network and then passes control to it.