Standard Rate Turn

A turn of three degrees per second. (PCG definition)
A turn in which an aircraft changes its direction at a rate of 3° per second (360° in 2 minutes) for low- or medium-speed aircraft. For high-speed aircraft, the standard rate turn is 1½° per second (360° in 4 minutes). (PHAK definition)

Source: PCG, Pilot Handbook of Aeronatical Knowledge