Flooding vs Unknown Unicast Flooding Can someone clarify what is the difference between **Flooding** and **Unknown Unicast Flooding**? Is it the same thing or it contains different meaning? I'm aware that Flooding happens when a switch receives a frame with a destination address that is not present in the switch's MAC table, so it replicates the received frame and sends it to all switch ports except the one from which it has received the frame.

As @ronmaupin points out, "flooding" is a generic term for sending data everywhere (usually except the source). OSPF multicasts link state advertisements, and we colloquially say OSPF floods them in an area.

Unknown Unicast Flooding, is a specific example of flooding, as you have accurately described in your question.