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 prosy: most prosy.

"The absence of the worker, through illness or death is sufficient to touch the prosiest workshop and tools with the hues of pathos, and it was with a swelling bosom that Lady Constantine passed through this arena of his youthful activities to the little chamber where he lay."