It depends on the audience.
If you're talking to us (the geeks, the readers of Sheldon Brown), it's a light roadster.
If you're talking to a civilian born before 1960, it's a touring bike.
If you're talking to a civilian born after 1960, it's a town bike, townie, or city bike.
If you're talking to a certain confused college student I talked to recently, it's a "pedestrian bike." Go figure.