Lewis & Short

prae-monstro (old form praemo-stro, v. infra), āvi, ātum, 1, v. a., to show beforehand, to point out the way, to guide, direct.

  1. I. In gen. (poet.): praemonstra docte, quid fabuletur, Plaut. Pers. 1, 3, 68: currenti spatium praemonstra, Lucr. 6, 93: te praemonstrante, under thy guidance, Stat. Th. 1, 66: praemostro tibi, ut, I caution you, that, Plaut. Trin. 2, 2, 61 Brix ad loc.: quae voluit mihi dixit, docuit et praemonstravit prius, id. ib. 4, 2, 12.
  2. II. In partic., to denote beforehand, to predict, presage, prognosticate: magnum aliquid populo Romano praemonstrare et praecinere, Cic. Har. Resp. 10, 21: ventos futuros, id. poët. Div. 1, 7, 13: hanc suavitatem praemonstratam efficaci auspicio, Plin. 10, 29, 43, § 82.

praemostro, old form of praemonstro, Plaut. Trin. 341.