resonator

noun

1. anything that resonates.
2. an appliance for increasing sound by resonance.
3. an instrument for detecting the presence of a particular frequency by means of resonance.
4. Electronics.
   1. a hollow enclosure (cavity resonator) made of conducting material of such dimensions that electromagnetic radiation of a certain frequency will resonate.
   2. any circuit having this frequency characteristic.

noun

1. any body or system that displays resonance, esp a tuned electrical circuit or a conducting cavity in which microwaves are generated by a resonant current