From Longman Dictionary of Contemporary Englishbriefcasebrief‧case /ˈbriːfkeɪs/ ●●○ noun [countable] 
BDa flat case used especially by business people for carrying papers or documents
BDa flat case used especially by business people for carrying papers or documentsExamples from the Corpus
briefcase• It had become compact enough to sit on a desk or slip into a briefcase.• He has also ditched his briefcase for a backpack to carry his dress shoes.• Simon Jay had his briefcase and cassette radio stolen from his car this morning.• Ivor thought she might have gone through his briefcase and found a letter from me.• I rammed my books and my binders into my briefcase.• He puts his green plastic briefcase on the desk.• Converse carried the briefcase through the hurrying evening crowds on Le Loi, walking as casually as he could.• Put a copy in your locked desk drawer and another in the secret compartment of your briefcase.From Longman Business Dictionarybriefcasebrief‧case /ˈbriːfkeɪs/ noun [countable]OFFICE a case used for carrying papers or documents 