Resonator \Res"o*na`tor\ (-n?`t?r), n. (Acoustics) Anything which resounds; specifically, a vessel in the form of a cylinder open at one end, or a hollow ball of brass with two apertures, so contrived as to greatly intensify a musical tone by its resonance. It is used for the study and analysis of complex sounds.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Resonator \Res"o*na`tor\, n. [NL. & G.]

Anything that resounds or resonates; specif.:
   (a) (Teleg.) An open box for containing a sounder and designed to concentrate and amplify the sound.
   (b) (Elec.) Any of various apparatus for exhibiting or utilizing the effects of resonance in connection with open circuits, as a device having an oscillating circuit which includes a helix of bare copper wire, a variable number of coils of which can be connected in circuit with a condenser and spark gap excited with an induction coil. It is used to create high-frequency electric brush discharges.
   (c) (Wireless Teleg.) The antenna system and other high-frequency circuits of a receiving apparatus.

Source: Webster's Revised Unabridged Dictionary (1913)