\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.]

\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.

\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.