OBO is an abbreviation that stands for "or best offer". It is commonly used in advertisements for possessions that people are trying to sell, to show that they will accept slightly less money than the sum they have mentioned. For example, if someone lists a car for sale as OBO, they are motivated to sell it and are willing to go lower than their listing price if need be, even if theyre still looking for the best possible offer. OBO can also imply that the seller will accept bids and receive a higher offer than the listed price.