The Collaborative International Dictionary of English v.0.48:

Devout \De*vout"\, a. [OE. devot, devout, F. d['e]vot, from L.
   devotus devoted, p. p. of devovere. See Devote, v. t.]
   1. Devoted to religion or to religious feelings and duties;
      absorbed in religious exercises; given to devotion; pious;
      reverent; religious.
      [1913 Webster]

            A devout man, and one that feared God. --Acts x. 2.
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            We must be constant and devout in the worship of
            God.                                  --Rogers.
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   2. Expressing devotion or piety; as, eyes devout; sighs
      devout; a devout posture. --Milton.
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   3. Warmly devoted; hearty; sincere; earnest; as, devout
      wishes for one's welfare.
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   The devout, devoutly religious persons, those who are
      sincerely pious.

   Syn: Holy; pure; religious; prayerful; pious; earnest;
        reverent; solemn; sincere.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Devout \De*vout"\, n.
   1. A devotee. [Obs.] --Sheldon.
      [1913 Webster]

   2. A devotional composition, or part of a composition;
      devotion. [Obs.] --Milton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

devout
    adj 1: deeply religious; "a god-fearing and law-abiding people"
           H.L.Mencken [syn: devout, god-fearing]
    2: earnest; "one's dearest wish"; "devout wishes for their
       success"; "heartfelt condolences" [syn: dear, devout,
       earnest, heartfelt]

Moby Thesaurus II by Grady Ward, 1.0:

108 Moby Thesaurus words for "devout":
   Christian, Christianlike, Christianly, abandoned, active, adorant,
   adoring, afire, ardent, assured, believing, burning, certain,
   churchgoing, committed, compliant, confident, conforming,
   conscientious, constant, convinced, cultish, cultist, cultistic,
   dedicated, devoted, devotional, dogmatic, doubtless, duteous,
   dutiful, earnest, faithful, fervent, fervid, fideistic, fiery,
   flaming, genuine, godly, heartfelt, hearty, heated, holy, hot,
   hot-blooded, impassioned, imploring, impressed with, in earnest,
   in the dust, intense, intent, intent on, loyal, meticulous,
   mindful, observant, on bended knee, on fire, passionate, perfervid,
   persuaded, pietistic, pious, pistic, positive, practicing,
   prayerful, precative, precatory, prostrate before, punctilious,
   punctual, pure, red-hot, regardful, religious, resolute, reverent,
   reverential, saintly, satisfied, scrupulous, secure, serious,
   sincere, sold on, solemn, spirited, staunch, suppliant, supplicant,
   supplicatory, sure, theistic, true, under the impression,
   undoubtful, undoubting, vehement, venerational, venerative, warm,
   white-hot, worshipful, worshiping, zealous