It is an antonym, actually. Briefs are detailed descriptions expressed in short notations for immediate exchange and action.
Going beyond the brief is expected, but not an accountable job description. When you apply yourself to the context, doing what it takes, you get the meaning of the brief.
Absence of a brief is when problems arise. Mis-communication, missed timelines, missed effort targets, missing quality points, can all be traced to the absence of a briefing session and brief document. A fundamental rule is to have a business brief, creative brief, technical architecture brief, lexicon brief, style guides, and like when you start an assignment.
Have you given a briefing session and documented the minutes anytime ? This is the basic "quality gate" that you need to pass for an effective project management.
How many documents you create and how many briefs you give during your projects? How successful has it been ? Looking forward to your answers in the comments section.