A device in an electric motor or generator that reverses the direction of current flow to keep the motor spinning, or in mathematics, a measure of how much two operations fail to commute.
From Latin commutatus plus -or (agent noun suffix). In electrical use, dates to the 1830s-1840s with early electric motor development.
The humble commutator—a split ring of copper that brushes slide against—was the breakthrough that made practical electric motors possible. Without it, you'd have no electric drills, fans, or toy motors!
Complete word intelligence in one call. Free tier — 50 lookups/day.