It is equal to one-half the length of the vibration path. amplitude synonyms, amplitude pronunciation, amplitude translation, English dictionary definition of amplitude. Amplitude definition is - the extent or range of a quality, property, process, or phenomenon: such as. See more. Amplitude definition, the state or quality of being ample, especially as to breadth or width; largeness; greatness of extent. amplitude definition: The definition of amplitude refers to the length and width of waves, such as sound waves, as they move or vibrate. Waves are generated by vibrating sources, their amplitude being proportional to … How to use amplitude in a sentence. n. 1. Amplitude, in physics, the maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. This helps us see another way to state the definition of amplitude, which is the vertical distance from a peak to the equilibrium position or from the equilibrium position to a valley. (noun) How much a radio … Define amplitude.