Haustorium \Haus*to"ri*um\ (h[add]s*t[=o]"r[i^]*[u^]m), n.; pl. {Haustoria} (h[add]s*t[=o]"r[i^]*[.a]). [LL., a well, fr. L. haurire, haustum, to drink.] (Bot.) One of the suckerlike rootlets of such plants as the dodder and ivy. --R. Brown. [1913 Webster]