mastermaster2 adjectiveadj [only before a noun]1master copy/ file/list etc the original thing from which copies are madeWhen a large number of copies of the same document are required, they can be photocopied from a master copy.
2master craftsman/builder/chef etcJOB someone who is very skilled at a job done with their hands and can teach it to other peopleThe company now uses semi-skilled operators instead of master bakers.
3the most important or main thingMr Bond’s master company, Bond Corporation