Proposed alteration of a creditor’s or equity interest holder’s legal, equitable, or contractual rights under a Chapter 11 plan. For example, a lender’s claim is an impaired claim if the plan modifies the maturity date, interest rate, or any provision of the lender’s loan documents even if the Chapter 11 plan provides for payment in full of the claim and even if the modification favors the lender (such as an increase in the contractual interest rate).
Bankruptcy Code § 1124. See also Artificial Impairment, Impaired Class, Non-Impairment Plan, One-Impaired-Class-Must-Accept-The-Plan Rule.