Liftoff is the moment when a rocket or spacecraft leaves the ground and begins rising into the air. During liftoff, the rocket's engines fire with tremendous force, creating enough thrust to overcome Earth's gravity and push the massive vehicle upward. Mission control counts down: “Three, two, one, liftoff!”

The word captures that critical instant when something that was sitting still suddenly breaks free and starts moving skyward. Watching a rocket at liftoff is unforgettable: flames shoot from the engines, the ground shakes, and thousands of tons of metal and fuel slowly, then quickly, climb toward space.

People also use liftoff to describe any moment when something finally starts after a period of preparation. A teacher might say a new school project has achieved liftoff when students get excited and dive into the work. A business might celebrate liftoff when its product finally reaches customers after months of development. The word always suggests that initial surge of energy and movement after everything has been made ready.