Mezzanine debt capital generally refers to that layer of financing between a company's senior debt and equity. Structurally, it is subordinate in priority of payment to senior debt, but senior in rank to common stock or equity. In a broader sense, mezzanine debt may take the form of convertible debt, senior subordinated debt or private "mezzanine" securities (debt or preferred equity).
Debt which ranks and is repaid after senior debt but before junior/institutional loan stock. Generally carries an option, warrant or redemption fee, which tends to distinguish it from senior debt reflecting the inherent risk nature of such a debt instrument.