Source : Webster's Revised Unabridged Dictionary (1913)

Relay \Re*lay"\, a. (Mach.)
   Relating to, or having the characteristics of, an auxiliary
   apparatus put into action by a feeble force but itself
   capable of exerting greater force, used to control a
   comparatively powerful machine or appliance. [Webster 1913
   Suppl.]

Relay \Re*lay"\ (r?-l?"), v. t. [imp. & p. p. {Relaid} (-l?d);
   p. pr. & vb. n. {Relaying}.] [Pref. re- + lay, v.]
   To lay again; to lay a second time; as, to relay a pavement.

Relay \Re*lay"\ (r?-l?"), n. [F. relais (cf. OF. relais
   relaxation, discontinuance, It. rilascio release, relief,
   rilasso relay), fr. OF. relaissier to abandon, release, fr.
   L. relaxare. See {Relax}.]
   1. A supply of anything arranged beforehand for affording
      relief from time to time, or at successive stages;
      provision for successive relief. Specifically:
      (a) A supply of horses placced at stations to be in
          readiness to relieve others, so that a trveler may
          proceed without delay.
      (b) A supply of hunting dogs or horses kept in readiness
          at certain places to relive the tired dogs or horses,
          and to continue the pursuit of the game if it comes
          that way.
      (c) A number of men who relieve others in carrying on some
          work.

   2. (Elec.) In various forms of telegraphic apparatus, a
      magnet which receives the circuit current, and is caused
      by it to bring into into action the power of a local
      battery for performing the work of making the record;
      also, a similar device by which the current in one circuit
      is made to open or close another circuit in which a
      current is passing.

   {Relay battery} (Elec.), the local battery which is brought
      into use by the action of the relay magnet, or relay.

Source : WordNet®

relay
     v 1: pass along; "Please relay the news to the villagers"
     2: control or operate by relay

relay
     n 1: the act of relaying something
     2: electrical device such that current flowing through it in
        one circuit can switch on and off a current in a second
        circuit [syn: {electrical relay}]