a series of persons relieving one another or taking turns; shift.
a fresh set of dogs or horses posted in readiness for use in a hunt, on a journey, etc.
Sports. relay race. a length or leg in a relay race.
Machinery. an automatic control device in which the settings of valves, switches, etc., are regulated by a powered element, as a motor, solenoid, or pneumatic mechanism actuated by a smaller, sensitive element.