What is the meaning of Buy_in?

Misspelling of buy-in.

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.

Source: wiktionary.org