We have been able to read it for days, weeks, every year, actually almost always, in writing, numbers or symbols:
Not just on the clothes rails or in the shoe rack. At H&M or Burberrys.
No, who would have thought it, as the title of a CD by Die Ärzte, "The Sell-Out Continues". Or in a book: "The Sell-Out of the Dark Continent". Even in the film "The Great Sell-Out" you come across the word "sell-out".
When you look it up in the dictionary, it is formulated simply and clearly: Aus/ver/kauf, the; complete sale of goods to clear the warehouse.