Abbreviation for Mint in Box which should mean the reel has only a tiny amount of shelf wear from age and never used. It should also be in the original box it was sold in. Serial numbers are very important to determine this as well as the correct spool and all other components. The problem with this is a lot of people use this term that have no idea what it means. Others that do know what it means TRY to make up “Frankenstein” reels MIB. Buyers Beware!