rectilinear UK /ˌɹɛktɪˈlɪnɪə/US /ˌɹɛktɪˈlɪniɚ/ adjective2 •In a straight line.The crankshaft and connecting rods of an engine convert the rectilinear motion of the pistons to rotary motion of the flywheel. •Formed from straight lines.10. A Chiltern Railways 2023 rectilinear diagram. — 2026 formsmore rectilinear · most rectilinear