Lewis & Short

ab-surdus, a, um, adj. [ab, mis-, and Sanscr. svan = sonare; cf. susurrus, and σῦριγξ, = a pipe; cf. also absonus], out of tune, hence giving a disagreeable sound, harsh, rough.

  1. I. Lit.: vox absona et absurda, Cic. de Or. 3, 11, 41; so of the croaking of frogs: absurdoque sono fontes et stagna cietis, Poët. ap. Cic. Div. 1, 9, 15.
  2. II. Fig., of persons and things, irrational, incongruous, absurd, silly, senseless, stupid: ratio inepta atque absurda, Ter. Ad. 3, 3, 22: hoc pravum, ineptum, absurdum atque alienum a vitā meā videtur, id. ib. 5, 8, 21: carmen cum ceteris rebus absurdum tum vero in illo, Cic. Mur. 26: illud quam incredibile, quam absurdum! id. Sull. 20: absurda res est caveri, id. Balb. 37: bene dicere haud absurdum est, is not inglorious, per litotem for, is praiseworthy, glorious, Sall. C. 3 Kritz.
    Homo absurdus, a man who is fit or good for nothing: sin plane abhorrebit et erit absurdus, Cic. de Or. 2, 20, 85: absurdus ingenio, Tac. H. 3, 62; cf.: sermo comis, nec absurdum ingenium, id. A. 13, 45.
    Comp., Cic. Phil. 8, 41; id. N. D. 1, 16; id. Fin. 2, 13.
    Sup., Cic. Att. 7, 13.
    Adv.: absurdē.
      1. 1. Lit., discordantly: canere, Cic. Tusc. 2, 4, 12.
      2. 2. Fig., irrationally, absurdly, Plaut. Ep. 3, 1, 6; Cic. Rep. 2, 15; id. Div. 2, 58, 219 al.
        Comp., Cic. Phil. 8, 1, 4.
        Sup., Aug. Trin. 4 fin.