Added 9 October 2026 expander noun Categories: Rare Words noun ! Definition from Wiktionary (CC BY-SA). More about expander at Wordnik → Where our words come from → One who or that which expands. A device used to widen the upper jaw so that the bottom and upper teeth will fit together better; a palatal expander. A control that expands to show more options or commands, keeping them hidden until needed. Related Words: extendermagnifiercompressorexpandorenlargerincreaserstretcherswellerexpatiatoroutstretcherextensionistexplicator Back to today's word