It stands for market-linked debenture; a structured product that constitutes a loan taken by a firm from the market that bears no fixed rate of interest. However, the return to the investor is linked to a specific market index like S&P. This means the financial performance of a debenture depends on that of the overall market index. The investors will be better off should the overall market performs well over the tenor of the loan.
A variation on an MLD is a PP-MLD (a principal-protected market-linked debenture).
