(1) A clause in a contract permitting an adjustment of certain payments either up or down in order to cover certain contingencies. In a lease contract, the escalator clause permits rent increases over the term of the lease, generally in accordance with a common index like the Consumer Price Index (CPI). In a mortgage, a lender is permitted to increase or decrease interest rates based on fluctuations in prevailing interest rates or the prime rate. (Definition adapted from John. W. Reilly?s The Language of Real Estate, published by Real Estate Education Company, Chicago.) (2) A moving stairway that carries passengers from one floor to another continuously.