Real Dictionary

relay
countable noun: A relay is a piece of equipment that receives television or radio signals from one place and sends them to another place.
countable noun: A relay or a relay race is a race between two or more teams, for example teams of runners or swimmers. Each member of the team runs or swims one section of the race.
verb: If you relay something that has been said to you, you repeat it to another person.
verb: To relay television or radio signals means to send them or broadcast them.

relay in American English
a fresh supply of dogs, horses, etc. kept in readiness to relieve others in a hunt, on a journey, etc.
to convey by relays

relay in American English 1
intransitive verb: to retransmit a signal or message electronically
noun: a series of persons relieving one another or taking turns; shift
transitive verb: to carry forward by or as if by relays

relay in American English 2
transitive verb

relay in Automotive Engineering
noun: A relay is a usually electrical device that switches on in response to a physical change, such as a pressure change or temperature change.

relay in British English
noun: a person or team of people relieving others, as on a shift
verb: to carry or spread (something, such as news or information) by relays

relay in Electrical Engineering
noun: A relay is an electromagnetic switching device that consists of an armature that is moved by an electromagnet to operate one or more switch contacts.

relay in Mechanical Engineering
noun: A relay is a device that controls the setting of a valve or switch automatically by means of an electric motor, solenoid, or pneumatic mechanism.