Rotating shafts in an engine that have shaped lobes (cams) which push on valves to open and close them at precise times.
From Middle Dutch 'cam' (mechanical part with a protruding shape) and English 'shaft' (rod), combined in automotive engineering in the early 1900s.
The camshaft is a genius piece of engineering—a single rotating rod with bumps coordinates when fuel enters and exhaust leaves an engine thousands of times per minute.
Complete word intelligence in one call. Free tier — 50 lookups/day.