1. a non-confrontational way to get someone to remember something
give a friendly reminder to someone
The term 'a friendly reminder' is generally used when the reminder isn't very friendly at all. You might get a 'friendly reminder' from a bank or a utility company about money you owe, or a Manager might email you with a 'friendly reminder' that your report is due on his desk first thing Monday morning. These are 'soft language' terms designed to conceal the true urgency of a request or demand by presenting it politely.