From Longman Business Dictionaryannual equivalent rateˌannual eˈquivalent ˌrate (abbreviation AER)FINANCE a rate of interest, which shows how much interest you receive from an investment in one year, if each interest payment is added to the deposit before the following year’s payment is calculatedWhen choosing a monthly interest account, look for the annual equivalent rate (AER). This gives the best picture of the account’s true rate. → rate