Lewis & Short

dē-mens, entis,

  1. I. adj., out of one’s mind or senses; mad, raving; foolish (cf. amens) (class. and very freq.; for syn. cf.: amens, excors, vecors, insanus, vesanus, delirus, alienatus mente): qua perturbatione animi quae, sanus cum esset, timebat ne evenirent, ea demens eventura esse dicebat, Cic. Div. 2, 55 fin.: summos viros desipere, delirare, dementes esse dicebas, id. N. D. 1, 34, 94 (for which, delirare et mente esse captum, id. Off. 1, 27, 94): ego te non vecordem, non furiosum, non mente captum, non tragico illo Oreste aut Athamante dementiorem putem, id. Pis. 20, 47; cf. Orestes, Hor. S. 2, 3, 133 and 135; 1, 6, 97; 1, 10, 74; id. Od. 1, 37, 7; Juv. 15, 1: Pentheus, Verg. A. 4, 469: in tranquillo tempestatem adversam optare dementis est, Cic. Off. 1, 24, 83; cf. id. Rep. 1, 1: quem fugis, ah, demens? Verg. E. 2, 60: non tacui demens, id. A. 2, 94 et saep.
  2. II. Poet. transf., of inanimate subjects: manus, Tib. 1, 10, 56: somnia, Prop. 3, 8, 15 (4, 7, 15 M.): furor, id. 1, 13, 20: discordia, Verg. A. 6, 280: falx, id. ib. 3, 7: strepitus, Hor. Od. 3, 19, 23: cura alieni pericli, Val. Fl. 6, 474: cf. ratio, Nep. Paus. 3, 1: otium, Plin. 2, 23, 21, § 85.
    Sup.: causa dementissimi consilii, Cic. Phil. 2, 22, 53; Auct. Harusp. resp. 26.
    Adv.: dēmenter, foolishly, madly (rare): tanta res tam dementer credita, * Cic. Cat. 3, 9, 22; Ov. M. 4, 259: dementissime testabitur, Sen. Ben. 4, 27 fin.