noun. ['dɪˌsɛlɝˈeɪʃən'] a decrease in rate of change.
noun. ['dɪˌsɛlɝˈeɪʃən'] the act of decelerating; decreasing the speed.
noun. ['dɪˌsɛlɝˈeɪʃən'] (physics) a rate of decrease in velocity.