dimout n darkness resulting from the extinction of lights (as in a city invisible to enemy aircraft) Usage(s) Sunday, Boston in the dimout, the Patagonian lakes, Virginia Woolf, Paul Valery. Clearest indication of the dimout is the unpublicized decision to change plans for Evita's mausoleum. The Administration is studying the idea of conserving coal by issuing a national dimout order. Synonym(s) blackout brownout