It stands for bugle bracket; a slang term that denotes the largest global banks that operate in all regions and offer all types of services to clients including mergers and acquisitions (M&A), equity and debt related services, etc. Such banks also have dedicated units and divisions for sales and trading, corporate banking, wealth management, equity research, and so on.

Bulge brackets usually undertake very big deals, usually with sizes exceeding $1 billion, depending on the market. By nature, bulge brackets have the highest volume of sales of initial public offerings (IPOs).

BB is also known as as BB firm or BB bank.