The Collaborative International Dictionary of English v.0.48:

Immodest \Im*mod"est\, a. [F. immodeste, L. immodestus
   immoderate; pref. im- not + modestus modest. See Modest.]
   1. Not limited to due bounds; immoderate.
      [1913 Webster]

   2. Not modest; wanting in the reserve or restraint which
      decorum and decency require; indecent; indelicate;
      obscene; lewd; as, immodest persons, behavior, words,
      pictures, etc.
      [1913 Webster]

            Immodest deeds you hinder to be wrought,
            But we proscribe the least immodest thought.
                                                  --Dryden.

   Syn: Indecorous; indelicate; shameless; shameful; impudent;
        indecent; impure; unchaste; lewd; obscene.
        [1913 Webster]

WordNet (r) 3.0 (2006):

immodest
    adj 1: having or showing an exaggerated opinion of your
           importance, ability, etc; "brash immodest boasting" [ant:
           modest]
    2: offending against sexual mores in conduct or appearance [ant:
       modest]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "immodest":
   aggressively self-confident, arrogant, bawdy, biggety, bold, brash,
   brazen, brazenfaced, bumptious, cheeky, chesty, coarse, cocky,
   conceited, dirty, disrespectful, exhibitionistic, flagrant,
   forward, fresh, impertinent, improper, impudent, indecent,
   indecorous, indelicate, insolent, know-it-all, lascivious, lewd,
   loose, notorious, obscene, obtrusive, overwise, peacockish,
   peacocky, perk, perky, pert, presumptuous, provocative, puffed up,
   revealing, self-conceited, self-opinionated, sexy, shameful,
   shameless, smart-alecky, smutty, stuck-up, swelled-headed,
   titillating, unabashed, unashamed, unblushing, unembarrassed,
   unmodest, unrestrained, wanton



The Devil's Dictionary (1881-1906):

IMMODEST, adj.  Having a strong sense of one's own merit, coupled with
a feeble conception of worth in others.

    There was once a man in Ispahan
        Ever and ever so long ago,
    And he had a head, the phrenologists said,
        That fitted him for a show.

    For his modesty's bump was so large a lump
        (Nature, they said, had taken a freak)
    That its summit stood far above the wood
        Of his hair, like a mountain peak.

    So modest a man in all Ispahan,
        Over and over again they swore --
    So humble and meek, you would vainly seek;
        None ever was found before.

    Meantime the hump of that awful bump
        Into the heavens contrived to get
    To so great a height that they called the wight
        The man with the minaret.

    There wasn't a man in all Ispahan
        Prouder, or louder in praise of his chump:
    With a tireless tongue and a brazen lung
        He bragged of that beautiful bump

    Till the Shah in a rage sent a trusty page
        Bearing a sack and a bow-string too,
    And that gentle child explained as he smiled:
        "A little present for you."

    The saddest man in all Ispahan,
        Sniffed at the gift, yet accepted the same.
    "If I'd lived," said he, "my humility
        Had given me deathless fame!"
                                                          Sukker Uffro