Resembling the mammoth in size; very large; gigantic; as, a mammoth ox.
source: Webster 1913
noun
any of numerous extinct elephants widely distributed in the Pleistocene; extremely large with hairy coats and long upcurved tusks
source: WordNet 3.0
An extinct, hairy, maned elephant (Elephas primigenius), of enormous size, remains of which are found in the northern parts of both continents. The last of the race, in Europe, were coeval with prehistoric man.
source: Webster 1913
adjective satellite
so exceedingly large or extensive as to suggest a giant or mammoth
A gigantic redwood. Gigantic disappointment. A mammoth ship. A mammoth multinational corporation.