when a lot of something is sold► sell · Books that don't sell are sent back to the publishers.· The handcrafted rocking horses have sold well across the United States.· The last model didn't sell as well as they'd expected.
► best-selling a best-selling product is one that is sold in large numbers, especially more than any other product of the same type: · Agatha Christie is said to be the world's best-selling author.· a list of the week's best-selling music and children's videos· Chanel Number 5 is the best-selling scent of all time.
► best-seller /bestseller/best seller a book, game, video, record etc that has been bought by a very large number of people: · Several TV movies have been based on best sellers by Danielle Steel.· Every year there's a toy that becomes a hard-to-find best-seller.bestseller list (=an official list of what has sold most): · All four Harry Potter books are currently on the bestseller list.
► outsell if one product outsells another, more of it is sold than the other product: · His latest album has outsold all his other records put together.· Chardonnay continues to outsell other wines.
► be selling like hot cakes informal if a product is selling like hot cakes , it is being sold very quickly and in large amounts because people very much want to buy it: · Grisham's new book is selling like hot cakes.
► do a roaring trade British if a shop or a person that sells a particular type of goods is doing a roaring trade , they are selling large quantities of goods because a lot of people suddenly want to buy them: · Since the heatwave started, ice cream vendors have been doing a roaring trade.do a roaring trade in: · The shops outside the station were doing a roaring trade in umbrellas.
1be selling/going like hot cakes if things are selling like hot cakes, they are very popular and a lot of people are buying them very quickly: 
Copies of the book are selling like hot cakes.2American English a pancake