When a company faces bankruptcy or liquidation, the claims of senior debt holders are prioritized over those of subordinated debt holders. Senior debt has the first claim on the company's assets and cash flows, meaning it must be paid back in full before any other debt or equity holders receive payment. Subordinated debt, also known as junior debt, is lower in the hierarchy and thus carries more risk.

Choice A is incorrect because subordinated debt ranks below senior debt in the event of winding up. Choice B is incorrect because subordinated debt holders receive interest payments, not dividends (which are for equity holders), and rank above equity holders, not alongside them. Choice D is incorrect as an increase in volatility generally transfers wealth from debt holders to equity holders in a structural model context, lowering the value of both senior and subordinated debt, but Choice C represents a direct and universally correct definition of subordinated debt.