wellingtonia UK /ˌwɛlɪŋˈtəʊ.ni.ə/US /ˌwɛlɪŋˈtoʊ.ni.ə/ noun2 •(UK) A large coniferous tree, Sequoiadendron giganteum, from California. •Wellingtonia arnottiana, now Meliosma arnottiana formswellingtonias