This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. superlative form of glum: most glum.

"A recent survey of 89 fund managers by Morgan Stanley showed that only a quarter of buy-side investors believe that India will beat other emerging markets this year, the glummest outlook in two years."