Meaning

noun a rheostat that varies the current through an electric light in order to control the level of illumination

adjective lacking in light; not bright or harsh

adjective lacking clarity or distinctness

originEtymology tree English dim Proto-Indo-European *-yósder. Proto-Italic *-āzijos Latin -āriusnom. Latin -āriusbor. Proto-Germanic *-ārijaz Proto-West Germanic *-ārī Old English -ere Middle English -ere English -er English dimmer From dim (verb) + -er.

Etymology from Wiktionary, CC BY-SA 3.0