—v.t. 1. to make evident or establish by arguments or reasoning; prove: to demonstrate a philosophical principle. 2. to describe, explain, or illustrate by examples, specimens, experiments, or the like: to demonstrate the force of gravity by dropping an object. 3. to manifest or exhibit; show: He demonstrated his courage by his actions in battle. 4. to display openly or publicly, as feelings: to demonstrate one's anger by slamming a door. 5. to exhibit the operation or use of (a device, process, product, or the like), usually to a purchaser or prospect: to demonstrate an automobile.
—v.i. 1. to make, give, or take part in, a demonstration: The pickets required a license to demonstrate. 2. Mil.to attack or make a show of force to deceive an enemy.