Briefly; to give the meaning of what has been said or written in a word or in a few words; in summary.
The children could play as long as they liked, they had no work to do, and nobody scolded them; in short, they were happy.
The speaker didn't know his subject, nor did he speak well; in brief, he was disappointing.
John is smart, polite, and well-behaved. In a word, he is admirable.