MICROCODE
firmware, microcode
(noun) (computer science) coded instructions that are stored permanently in read-only memory
Source: WordNet® 3.1
Etymology
Noun
microcode (usually uncountable, plural microcodes)
(computing) The collective microprograms in a CPU, used to run machine instructions.
Verb
microcode (third-person singular simple present microcodes, present participle microcoding, simple past and past participle microcoded)
(computing, transitive) To write or rewrite (program instructions) in microcode, typically to optimize performance.
Source: Wiktionary