Boulevard has at least two generally accepted meanings.

As a type of road, a boulevard usually consists of a wide, multi-lane arterial divided thoroughfare, often with an above-average appearance in terms of landscaping and scenery. Baron Haussmann made such roads well-known in his re-shaping of Second Empire Paris between 1853 and 1870. The French word boulevard originally referred to the flat summit of a rampart (the etymology of the word distantly parallels that of bulwark ). Many Parisian boulevards replaced old city walls.

However, in many places in the United States, particularly California, developers have adapted the term to refer to any arterial roads, not necessarily boulevards in the conventional sense. Many so-called "boulevards" in California extend into the mountains, with narrow, winding road segments only two lanes in width.

Some people also use the term boulevard to refer to the division or central reservation in such a road, whether specifically in a "boulevard" in the above sense or not. It can consist of anything from a simple thick curb of concrete, to a wide strip of grass, to a thoroughly landscaped space of trees, shrubs, and other foliage; in urban areas, boulevards can also contain public art or memorials. Wide boulevards also sometimes serve as rights-of-way for trams or light rail systems.