Accelerate : (especially of a vehicle) begin to move more quickly.Check : examine (something) in order to determine its accuracy, quality, or condition, or to detect the presence of something.Control : the power to influence or direct people's behaviour or the course of events.Slacken : reduce or decrease in speed or intensity.Supervise : observe and direct the execution of (a task or activity).Antonym of Accelerate is Slacken