buy in

Noun

• Alternate spelling of buy-in

Verb

• To accept an idea as valid; to join in on a concept.
• To invest as part of a group; to put one's personal stake in an investment.
• To buy back for the owner at an auction.
• For the buyer of securities, whose seller fails to deliver the securities contracted for, to buy the securities from a third party and demand the difference in price from the original seller.