A more thorough explanation:

An outer barrister is a type of lawyer in England or Northern Ireland who has been admitted to plead at the bar but is not called to plead from within it, unlike a Queen's Counsel or a serjeant-at-law. This means that they are not allowed to argue cases in superior courts from within the bar.

For example, a barrister who has been called to the bar but has not been appointed as a Queen's Counsel or a serjeant-at-law is an outer barrister. They are still qualified to practice law, but they cannot argue cases from within the bar.

Another example is a vacation barrister, who is a newly called barrister that must attend inn-of-court functions during the long vacation for at least three years. They are also considered outer barristers.

These examples illustrate the definition of an outer barrister by showing that they are barristers who have been called to the bar but are not allowed to argue cases from within it. They are still important members of the legal profession, but they have certain limitations on their practice.