ivory: the hard smooth yellowish-white substance from the tusks (=long teeth) of an elephant--Longman Dictionary of Contemporary English ivory:The hard, white, elastic, and fine-grained substance (being dentine of exceptional hardness) composing the main part of the tusks of the elephant, mammoth (fossil n. and adj.), hippopotamus, walrus, and narwhal; it forms a very valuable article of commerce, being extensively employed as a material for many articles of use or ornament.--Oxford English Dictionary  @en