Source : Webster's Revised Unabridged Dictionary (1913)

Haustorium \Haus*to"ri*um\, n.; pl. {Haustoria}. [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.

Source : WordNet®

haustorium
     n : a rootlike attachment in parasitic plants that penetrates
         and obtains food from the host
     [also: {haustoria} (pl)]