quaternary

Consisting of four; in fours.

Of, relating to, or being the period of geologic time from about 1.8 million years ago to the present, the more recent of the two periods of the Cenozoic Era. It is characterized by the appearance and development of humans and includes the Pleistocene and Holocene Epochs.

Relating to a nonhydrogen atom bonded to four other nonhydrogen atoms, especially to four carbon atoms.

The number four.

The member of a group that is fourth in order.

The Quaternary Period.

Fourfold or tetragonal: said of the symmetry of crystals. See symmetry, 6.

Consisting of four; arranged or grouped in fours.

[capitalized] In geology, noting that part of the geological series which is more recent than the Tertiary; Post-tertiary. (See Tertiary.)

In old chemistry, noting those compounds which contained four elements, as fibrin, gelatin, etc.