tertiary

adjective

1. not comparable Of third rank or order; subsequent. Beſides theſe primordial mountains, M. [P[eter] S[imon]] Pallas maintains, that there are others of a more recent origin. These he calls ſecondary and tertiary: […] the latter ariſe from the wrecks and contents of the ſea, raiſed and tranſported by volcanic eruptions and conſequent inundations.
2. not comparable Possessing some quality in the third degree; especially having been subjected to the substitution of three atoms or radicals. a tertiary alcohol, amine, or salt
3. not comparable Of quills: growing on the innermost joint of a bird's wing; tertial. The primary, secondary, and tertiary wing feathers (remiges) of adult mourning doves are shed and replaced yearly in an orderly sequence, so flight is possible during molt. […] Little is known about the shedding sequence of the secondary or tertiary feathers or the related coverts. If it is similar

Similar: ternary, tertial

noun tertiaries

1. Any item considered to be of third order. The primary rhizomes usually die during the growing season. The tertiaries and secondaries, however, live through the winter and become primary rhizomes the following year.
2. A tertiary colour. My principal objection is against the compound or derivative tints, given under the denominations of secondaries and tertiaries.
3. Something from the Tertiary Period (the former term for the geologic period from 65 million to 2.58 million years ago). There is, within our area, a great gap between the Eocene group and the later tertiaries, indicated by the difference of their organic contents. Between the existing fauna of our seas and the oldest stage of the later tertiaries, there is a distinct and extensive relationship of identity of species.
4. A tertiary feather; a tertial. The feathers [of the least sandpiper (Calidris minutilla)], black centrally, are margined with bright rufous, especially on the back, scapulars, and tertiaries, and with white tips on the latter; the stripes on the middle of the throat and chest are indistinct or almost absent, more evident on sides
5. A large stage in some extremely powerful thermonuclear weapons (resembling a greatly-enlarged secondary) which is compressed by the explosion of the secondary until ignition of nuclear fusion takes place, in much the same manner as the secondary is imploded by the primary, and which can allow for the attainment of yields of many tens or even hundreds of megatons, and likely even greater; not used in modern weapons due to a greater focus on the accurate use of sub-megaton weapons, the tremendous size of weapons incorporating a tertiary, and the lack of targets whose destruction would necessitat A gigaton-scale weapon would of necessity be a three-stage design (incorporating a fusion tertiary - likely with its own massive fission tamper - in addition to the fission primary and fission-jacketed fusion secondary), as a reasonably-sized primary would likely have difficulty imploding to ignitio
6. A member of a Roman Catholic third order; a layperson who participates in activities similar to those engaged in by men and women who take religious vows (respectively the first and second orders), and who may wear some elements of an order's habit such as a scapular. Tertiaries living in places where there is no Church of the Order or of the Third Order can gain all the indulgences they would gain visiting such a church, by visiting their respective parish church, or, where there is no parochial church, by visiting another church or public oratory, and fulfillin

adjective

1. not comparable Of or pertaining to the first part of the Cenozoic era when modern flora and mammals appeared.

proper noun

1. The first part of the Cenozoic era when modern flora and mammals appeared. […] a continental northern Alaskan element, including a series of endemic species and disjuncts that have survived the Pleistocene glaciation in northern Alaska and thus represent relicts of the much warmer Tertiary […]