Consisting of four; by fours, or in sets of four.
- Consisting of four; in fours.
- Of or belonging to the geologic time, system of rocks, or sedimentary deposits of the second period of the Cenozoic Era, from the end of the Tertiary Period through the present, characterized by the appearance and development of humans and including the Pleistocene and Holocene epochs. See Table at geologic time.
- Chemistry Relating to an atom bonded to four carbon atoms: a quarternary nitrogen atom.
- The number four.
- The member of a group that is fourth in order.
- The Quaternary Period or its system of deposits.