Inclined to gamble; willing or eager to take risks and play games of chance.
From gamble plus the archaic English suffix -some (characterized by, full of), creating an adjective meaning 'characterized by gambling or risk-taking.'
The suffix '-some' is mostly dead in English now (except in words like 'awesome' and 'handsome'), so 'gamblesome' is delightfully archaic—imagine calling someone 'murderous' instead of 'murderous'!
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