megatherial,a.|mɛgəˈθɪərɪəl| [f. megatheri-um + -al1.] Resembling the megatherium; in quots.fig., ponderous, unwieldy. 1894Nature 26 July 301 The disorderly offspring of a quite megatherial wit.1898H. G. Wells Cert. Personal Matters 82 A vast edifice..with which a Megatherial key was identified.