Gunboat diplomacy is an aggressive, showy kind of foreign policy. When a country employs gunboat diplomacy, it uses its military power to force other nations to do what it wants them to do.
If a government’s military might is on display in foreign countries, that’s gunboat diplomacy. The term was coined during the 19th century, when Western powers rushed to colonize parts of Asia and Africa for trading. When actual diplomacy didn't influence smaller countries to do their bidding, the U.S. and European forces would sail in fleets of warships (or gunboats) as a warning. Demonstrating military power is seen as one way to avoid war, and gunboat diplomacy is still used today.