Thriving business; a shop or trade doing well with many customers and strong sales. Also used as a phrase wishing prosperity.
新年の商店街では商売繁盛を願って笹を飾る店が多い。
In the shopping street at New Year many shops decorate bamboo branches praying for prosperous business.
今年は景気が良くてうちの店は商売繁盛だ。
This year the economy is good and our shop is thriving.
祭りののぼりに『商売繁昌』と大きく書かれていた。
The festival banners had 'shoubai hanjou' written big on them.