1. To betray one for a personal benefit. A noun or pronoun can be used between "sell" and "out." Part of the discontentment among voters comes from the sentiment that those in government sold them out when the economy collapsed. Jacob sold out the others to the police so that he would avoid jail time.

2. For a stock of something to become completely depleted due to every item having been sold. The tickets sold out in a matter of minutes. The new console is expected to sell out in minutes after it goes on sale.

3. To abandon or betray one's espoused principles or cause, especially in the pursuit of profit or personal benefit. Many of his fans felt he sold out when he signed with a major record label. That's it? One hard month and you're ready to sell out and get a corporate job?