A tarmac is a paved surface at an airport where planes taxi, park, and prepare for takeoff. When you board an airplane, you're walking out onto the tarmac, or driving across it in one of those shuttle buses. Pilots taxi their aircraft along the tarmac to reach the runway, and ground crews use it to service planes between flights.

While modern airports often use concrete or asphalt rather than actual tarmac material, people still use the word to describe any paved airport surface. When news reporters say a plane is “sitting on the tarmac,” they mean it's on the ground at the airport but not at a gate. The tarmac is essentially the airplane's road, the hard surface that lets these massive machines move around safely when they're not flying thousands of feet in the air.