Archaic or dialectal term meaning cheerful, merry, or characterized by gaiety; festive in nature.
From gay (happy) plus -some, an archaic suffix forming adjectives meaning 'having the quality of' or 'characterized by.' This formation was more common in older English.
The -some suffix produced lots of descriptive words in Middle and Early Modern English—'fearsome' and 'awesome' survived, but 'gaysome' didn't. It shows how productive word-formation processes can fade when their products go out of fashion.
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