Series definition1. A particular type of an automobile make and model. For instance, in 1952 Cadillac fielded three series: a 62 (with a 126 inch wheelbase ); a 60 (with a 130 inch wheelbase); and a 75 (with a 147 inch wheelbase).
2. The alignment of electrical components. See series circuit .
3. A numerical representation of a tire's aspect ratio. A 50-series tire has an aspect ratio of 0.50.