If you say that something is a particular amount maximum, you mean that this is the greatest amount it should be or could possibly be, although a smaller amount is acceptable or very possible. In mathematical analysis, the maximum and minimum[a] of a function are, respectively, the greatest and least value taken by the function. MAXIMUM definition: the greatest quantity or amount possible, assignable, allowable, etc. See examples of maximum used in a sentence. The meaning of MAXIMUM is the greatest quantity or value attainable or attained. maximum meaning, definition, what is maximum: the maximum amount, quantity, speed etc.: Learn more. MAXIMUM definition: 1. being the largest amount or number allowed or possible: 2. the largest amount allowed or…. Learn more. The simple definition of MAXIMUM is the highest number or amount that is possible or allowed—usually singular —often + of. MAXIMUM meaning: 1. being the largest amount or number allowed or possible: 2. the largest amount allowed or…. Learn more. Both a noun and an adjective, maximum takes it to the max: it means the most, the fastest, the biggest. 1. the highest amount, value, or degree attained or attainable. 2. an upper limit allowed by law or regulation.