means The paved surface of an airport runway, taxiway, or apron — or, more loosely, any asphalt road or aircraft parking area where planes and cars roll.

from A shortening of 'tarmacadam,' itself a blend of 'tar' and the surname of John Loudon McAdam, the road engineer whose method of layering crushed stone — 'macadam' — paved much of the 19th-century world. Spray that gravel surface with tar to bind it and keep the dust down, and you have tarmacadam, soon clipped to the brisker 'tarmac.' Tarmac became a registered trademark, but the word escaped into everyday speech the way trademarks often do, until any stretch of airport asphalt was simply 'the tarmac.'