百花繚乱
A hundred flowers blossom riotously.
... いろいろの花が咲き乱れること。転じて、秀でた人物が多く出て、すぐれた立派な業績が一時期にたくさん現れること。▽「百花」は種々の多くの花、いろいろな花の意。「繚乱」は花などがたくさん咲き乱れている様子。いろいろな花が、はなやかに美しく咲き乱れることから。
"A hundred flowers" (百花) refers to the flowers that are many and various.
In short, it refers to when distinguished people appear en masse to accomplish many great feats within a certain time period.
"Profusion" (繚乱) refers to the state of many flowers blooming, as derived from the beautiful but ephemeral sight of flowers blooming in unison.