Lewis & Short

dē-līro, āre, v. n. [de-lira, to go out of the furrow; hence],

  1. I. Lit., to deviate from a straight line: nil ut deliret amussis, Aus. Idyll. 16, 11; cf. Plin. 18, 20, 49, § 180.
  2. II. Trop. (cf. Vel. Long. p. 2233 P.), to be crazy, deranged, out of one’s wits; to be silly, to dote, rave (class.): delirat linguaque mensque, Lucr. 3, 454: falli, errare, labi, decipi tam dedecet quam delirare et mente esse captum, Cic. Off. 1, 27, 94; so with desipere and dementem esse, id. N. D. 1, 34, 94: Am. Delirat uxor. So. Atra bili percita est, Plaut. Am. 2, 2, 95 sq.: senex delirans, Ter. Ad. 4, 7, 43: morbo delirantes, Lucr. 5, 1158; cf. timore, Ter. Ph. 5, 8, 8: in extis totam Etruriam delirare, Cic. Div. 1, 18, 35: Stertinium deliret acumen, Hor. Ep. 1, 12, 20.
    With acc. respect.: quicquid delirant reges plectuntur Achivi, whatever folly the kings commit, id. ib. 1, 2, 14.