1. short in size or time
Something ‘brief’ is short in size or time. ‘A brief summary’ is a short summary, and a ‘brief speech’ is one which we understand will be over quickly. This adjective can be used in social and professional contexts.
2. summarize or explain instructions to another
brief them on the new criteria
When you use 'brief' as a verb, it means that you provide a summary or a short description of something. 'Brief' can also be a noun, as you can give someone their 'brief', which is a short overview of their duties or responsibilities. You are more likely to hear the verb and noun of 'brief' in a professional context.