Buyback is a term used to describe the process of a company or individual buying back their own stock from shareholders. It is often done to reduce the number of outstanding shares, increase the value of remaining shares, or to provide liquidity to shareholders. The term GUN is a 3 letter solution for the crossword and is an acronym for 'Give Up Now'. This phrase is often used in the context of buybacks, as it implies that shareholders should accept the offer and sell their shares.