nounthe opposite side to the front ExamplesWrite your address on the back of the envelope. • Please endorse the cheque on the back.adjectivereferring to the past Examplea back paymentadverbso as to make things as they were before ExamplesHe will pay back the money in monthly instalments. • The store sent back the cheque because the date was wrong. • The company went back on its agreement to supply at £1.50 a unit.verbto help someone, especially financially ExamplesThe bank is backing us to the tune of $10,000. • She is looking for someone to back her project.Usageto back a billto sign a bill promising to pay it if the person it is addressed to is not able to do so"...the businesses we back range from start-up ventures to established companies in need of further capital for expansion" [Times] referring to the past so as to make things as they were before the opposite side to the front to help someone, especially financially