cavern UK /ˈkav.ən/US /ˈkæv.ɚn/noun 3verb 2forms 3 noun3 •A large cave. •An underground chamber.In Xanadu did Kubla Khan / A stately pleasure-dome decree: / Where Alph, the sacred river, ran / Through caverns measureless to man / Down to a sunless sea. — 1797 •A large, dark place or space. verb2 •To form a cavern or deep depression in. •To put into a cavern. formscaverned · caverning · caverns