<p><strong>Adjective</strong></p><ul><li>Consisting of four.</li><li>Arranged in fours.</li><li>(Initial capital letter) Geology: Noting or pertaining to the present period of earth history, forming the latter part of the Cenozoic Era, originating about 2 million years ago and including the Recent and Pleistocene Epochs.</li><li>Metallurgy: (Of an alloy) having four principal constituents.</li></ul><p><strong>Noun</strong></p><ul><li>A group of four.</li><li>The number four.</li><li>(Initial capital letter) Geology: The Quaternary Period or System.</li></ul>