a twining, South American bean plant, Phaseolus coccineus, having clusters of scarlet flowers.
Origin
1780-90
British Dictionary definitions for scarlet runner
scarlet runner
noun
1.
a climbing perennial bean plant, Phaseolus multiflorus (or P. coccineus), of tropical America, having scarlet flowers: widely cultivated for its long green edible pods containing edible seeds Also called runner bean, string bean