Source : Webster's Revised Unabridged Dictionary (1913)

Megathere \Meg"a*there\, Megatherium \Meg`a*the"ri*um\, n. [NL.
   megatherium, fr. Gr. me`gas great + thyri`on beast.]
   (Paleon.)
   An extinct gigantic quaternary mammal, allied to the
   ant-eaters and sloths. Its remains are found in South
   America.

Source : WordNet®

Megatherium
     n : type genus of the Megatheriidae [syn: {genus Megatherium}]