Lewis & Short

prŏgnōstĭcon or -um, i, n., = προγνωστικόν, a sign or token of the future, a prognostic; hence, prŏgnōstĭca, ōrum, n., the signs of the weather, Quint. 5, 9, 15.
Also as the title of Cicero’s translation of the Προγνωστικά of Aratus, Cic. Div. 1, 8, 13; v. the fragments, id. Op. v. XI. p. 96 sqq. B. and K.