- a device for producing resonance or increasing sound by resonance
- an acoustic guitar with a circular metal device of this kind, rather than the traditional wooden soundboardin full resonator guitar
- Electronics an apparatus or system, as a piezoelectric crystal or a circuit, capable of being put into oscillation by oscillations in another system
- A resonating system.
- A hollow chamber or cavity with dimensions chosen to permit internal resonant oscillation of electromagnetic or acoustical waves of specific frequencies.
- A resonant circuit.