The phrase 'ad infinitum' conveys the concept of something continuing indefinitely, with no limits on the duration of time or amount of money it involves. An example could be a perpetual annuity of payments made by a company to an individual, where the individual receives payments indefinitely.
An undated security is a fixed-interest security that does not have a redemption date. These securities perpetually generate a set interest payment without a requirement for the principal to be returned at a specific future date.
