Definition of "prognostic"

There are several opinions as to what he meant But no one considers it a happy prognostic.

1935, T.S. Eliot, Murder in the Cathedral, Part I

The appearance of the tongue is closely connected with the sense of thirst, and is of considerable importance as a prognostic.

1809, Bartholomew Parr, “PROGNOSIS”, in The London Medical Dictionary

Careful observers may foretell the hour (By sure prognostics) when to dread a show’r. While rain depends, the pensive cat gives o’er Her frolics, and pursues her tail no more.

1710, Jonathan Swift, A Description of a City Shower

It was even later than usual when the Comtesse quitted a brilliant réunion of all that was gayest in the royal circle, elate with the glittering triumph of gratified vanity, and reading in such success the sure prognostic of more solidly successful ambition.

1834, L[etitia] E[lizabeth] L[andon], chapter XXIX, in Francesca Carrara. […], volume II, London: Richard Bentley, […], (successor to Henry Colburn), page 305

The choice of a successor was no light matter. That choice would inevitably be considered by the country as a prognostic of the highest import.

1849–1861, Thomas Babington Macaulay, chapter 11, in The History of England from the Accession of James the Second, volumes (please specify |volume=I to V), London: Longman, Brown, Green, and Longmans