Noun
a cannon or similar gun that fires harpoons
Source: WordNetNever mind what you were doing, Olaf said. You're fired! You can't fire me! Esme growled. I quit! Well, you can leave by mutual agreement, Olaf grumbled and then with another succinct Ha! he lifted the harpoon gun and pointed it at Dewey Denouement. Daniel Handler
Although it was initially cumbersome and had a low success rate, Foyn perfected the harpoon gun, and soon several whaling stations were established on the coast of Finnmark in northern Norway. Source: Internet
With his harpoon gun and his diving equipment he is able to spend hours underwater without worrying about oxygen supply or about danger he may encounter at sea. Source: Internet