From Longman Business Dictionaryfirst in, first outfirst ˌin, first ˈout abbreviation FIFO noun [uncountable]1ACCOUNTINGFINANCE a method of calculating the value of goods or materials a company has in stock, based on the idea that those put in stock first were the first ones sold or used. Any stock that is left at the end of the year is valued at the cost of the most recently bought stockSince inventory is costed on a first in, first out basis it is assumed the oldest inventory is used up first, leaving the newest inventory to be priced at the current higher prices. → compare last in, first out2MANUFACTURING a method of controlling stock in which the first items to be produced or bought are the first ones to be used or sold3COMPUTING a system in which a computer begins to process its instructions in the exact order in which they are received4HUMAN RESOURCES a principle sometimes used when a company has to make people redundant, which says that the first people to have started working there will be the first ones to lose their jobs