adj

• (obsolete) Rife; common; prevalent.

noun

• (law) A writ summoning one to answer; an official letter or mandate.
• (law) A writ summoning one to answer; an official letter or mandate.
  "It was in vain that the bishop published a new papal brief, declaring valid the excommunications which he had issued, and those of the inquisitors to be null, and requiring them to seek absolution from him."
• (law) An answer to any action.
  "A written answer or any other brief shall be submitted to the court while allowing a period necessary for the opponent to make preparations with regard to the matters stated therein."
• (law) A memorandum of points of fact or of law for use in conducting a case.

verb

• (transitive) To summarize a recent development to some person with decision-making power.
  "The U.S. president was briefed on the military coup and its implications on African stability."
• (transitive, law) To write a legal argument and submit it to a court.

adv

• (obsolete, poetic) Briefly.
  "Whence Adam faultring long, thus anſwer’d brief."
• (obsolete, poetic) Soon; quickly.
  "But that a ioy paſt ioy, calls out on me, / It were a griefe, to briefe to part with thee : / Farewell."