1 The financial obligations held by a dealer or an institution trading on financial markets. See book; making a book.
2 The consolidation of a bank's trading activities and obligations as opposed to its banking obligations. These are those activities of a bank that are seen as financial-market-related and short term. They are required to be marked to market (see marking to market) or marked to model (see marking to model) and must have adequate capital backing. Compare banking book.