parallel parallelbeing an equal distance apart everywhere, extending in the same direction, never meeting or intersectingRelated Articles: Glossary: plane waveDOSITS VideosTutorial: What is Sound?Science Tutorial: What is Sound?What is sound?GeophoneSounds Associated with AggressionLeopard SealHarbor Porpoise Derek Sutcliffe2017-02-26T20:10:00+00:00