harpoon UK /hɑːˈpuːn/US /hɑːɹˈpuːn/noun 3verb 1forms 3 noun3 •A spearlike weapon with a barbed head used in hunting whales and large fish. •(slang) A harmonica.I took my harpoon out of my dirty red bandana. — 1969 •A sharp tip within a disposable syringe, used to penetrate the stopper. verb1 •To shoot something with a harpoon.Pilot whales, also known as blackfish, were fairly plentiful, and Mundus would harpoon one or two, haul them out onto the beach, and butcher them. — 1983 formsharpooned · harpooning · harpoons