Resonator

It could reasonably be argued that all Ukuleles, for that matter all Chordophones are "Resonators" as all of them rely on resonance from the strings to create a sound, but for the purposes of this Wiki there are two distinct and specific meanings for the term "Resonator"; Banjo Resonators and "Resonator Instruments"

Banjo Resonator
When talking about Banjo type instruments the term "Resonator" is used to describe the, usually removable, flat plate or dish connected to the back of the drum with a small gap between it and the drum.