What does macadam mean?
Macadam is a paved road surface made from small broken stones held together with tar or bitumen. It can also refer more broadly to the technique of constructing such a surface, especially in the phrase “macadam road.” The word is chiefly associated with older road engineering, although it remains understandable in technical, historical, and regional contexts. Its name comes from the Scottish engineer John Loudon McAdam, who pioneered a method of building durable roads from compacted layers of crushed stone. The term is easily confused with “tarmac” and “asphalt”: macadam more specifically identifies the crushed-stone construction method, while the other terms are commonly used for tar- or bitumen-based paving materials. In everyday British and American English, “tarmac” and “asphalt” are generally more familiar, but “macadam” has the advantage of preserving a clear reference to a historically important form of road building.
nounA road surface made of small broken stones bound together with tar or bitumen. The term can also refer to the method of constructing such a surface.
- A road surface made of small broken stones bound together with tar or bitumen.
- The road-building method involving compacted layers of broken stone and binding material.
"The old road was resurfaced with macadam, giving it a smoother and more durable surface."
"Workers spread macadam across the lane and compacted it with heavy rollers."
"The construction manual described a durable macadam base for the new road."
The plural is used for multiple roads or surfaces of this type and is relatively uncommon.
"Several macadams were built along the new route."
The everyday word “macadam” preserves the name of Scottish engineer John Loudon McAdam, whose road-building method helped transform travel in the early nineteenth century.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does macadam come from?
The word comes from the surname of Scottish engineer John Loudon McAdam, whose method of road construction used compacted layers of broken stone. His name was anglicized in the early nineteenth century to “macadam,” and the term came to denote both the construction method and the finished road surface. The related word “macadamize” was formed by adding a verb suffix, while “tarmac” developed as a blend of “tar” and “macadam.”
Related word forms
How macadam is actually used
The term is chiefly used for a traditional crushed-stone road surface and is somewhat technical or historical in modern British and American English. In general use, “tarmac” and “asphalt” are often preferred.
Easily confused with macadam
Macadam specifically refers to broken stone bound with tar or bitumen, while tarmac is a broader term for tar-based paving and can also mean asphalt.
Asphalt generally refers to a bituminous paving material, whereas macadam traditionally means a layer of crushed stone bound with bitumen.