Superlative form of gloomy: most gloomy.(adjective)
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Use "gloomiest" in a sentence
"The gloomiest was my first day of college when my father died."
"Even the more "serious" papers seem to feature the gloomiest news on their front pages!"
"British households are at their gloomiest since the recession, according to a report released on Wednesday that will send further shockwaves through retailers already braced for a tough start to the new year."