The definition of a follow-up is a return to an existing situation or to a situation that is underway in order to determine what the current status is and whether all has been done or is being done.(noun)
An example of a follow up phone call is a telephone call made to check on the status of an order placed a week prior.
See follow-up in Webster's New World College Dictionary
See follow-up in American Heritage Dictionary 4
Learn more about follow-up