Noun
parallel motion
(engineering) Any linkage by which circular motion may be changed into motion in a straight line.
He acquired a taste for parallel motion in fifths, fourths and octaves from medieval music, and an appreciation for figuration and arabesque from the Baroque masters. Source: Internet
Its distinguishing factor is that the parts did not have to move only in parallel motion, but could also move in oblique, or contrary motion. Source: Internet