a county of S England, consisting mainly of chalk uplands, with Salisbury Plain in the south and the Marlborough Downs in the north; prehistoric remains (at Stonehenge and Avebury); became a unitary authority in 2009: the geographical and ceremonial county includes Swindon unitary authority (established in 1997). Administrative centre: Trowbridge. Pop (excluding Swindon): 440 800 (2003 est). Area (excluding Swindon): 3481 sq km (1344 sq miles)