SMB is an abbreviation for small and medium-sized business, sometimes seen as small and midsized business. A business with 100 or fewer employees is generally considered small, while one with 100-999 employees is considered to be medium-sized. SMB also stands for 'Server Message Block' in the Server Message Block Protocol. CERTIFICATES OF DEPOSIT BY SALLIE MAE. Financial services, namely, issuance and management of certificates backed by loan portfolios which are.