An electrical switch, in a generator or motor, that periodically reverses the direction of an electric current.
A binary map in a given group G, given by [g, h] = ghg⁻¹h⁻¹, where g and h are elements of G, which yields the group's identity if and only if the group operation commutes for g and h.
A binary map in a given ring R, given by [a, b] = ab − ba, where a and b are elements of R, which yields the ring's zero element if and only if the multiplication operation commutes for a and b.
A bistable; an electronic switching circuit that has either two stable states (switching between them in response to a trigger) or a stable and an unstable state (switching from one to the other and back again in response to a trigger), and which is thereby capable of serving as one bit of memory.
A return trip.
A sandal consisting of a rubber sole fastened to the foot by a rubber thong fitting between the toes and around the sides of the foot.
An instance of flip-flopping, of repeatedly changing one's stated opinion about a matter.
A change of places; an inversion or swap.
The sound of a regular footfall.
A somersault.
To alternate back and forth between directly opposite opinions, ideas, or decisions.