extending in the same direction, equidistant at all points, and never converging or diverging: parallel rows of trees.
having the same direction, course, nature, or tendency; corresponding; similar; analogous: Canada and the U.S. have many parallel economic interests.
Geometry. (of straight lines) lying in the same plane but never meeting no matter how far extended. (of planes) having common perpendiculars. (of a single line, plane, etc.) equidistant from another or others (usually followed by to or with).
Electricity. consisting of or having component parts connected in parallel: a parallel circuit.
Music. (of two voice parts) progressing so that the interval between them remains the same. (of a tonality or key) having the same tonic but differing in mode.