Macadam is a road surface made of broken stones mixed with tar or asphalt and packed hard so cars can run on it. It is named after a Scottish engineer, John Loudon McAdam (1756–1836), who invented a way of building roads from layers of small stones. His first roads did not use tar; later people added tar, and the name stayed. Today speakers sometimes use macadam for any black stone-and-tar street, or even loosely for “the road” itself, which is a bit stretched. You will see the word in older books, in engineering, and in talk about streets more than in daily chat — most people now say the road or, in Britain, tarmac. There is also a verb, to macadam a road, meaning to put that surface on it, but that verb is uncommon now.

碎石路面（柏油／瀝青碎石；源自工程師 McAdam 的鋪路法）