The Collaborative International Dictionary of English v.0.48:

Allege \Al*lege"\ ([a^]l*l[e^]j"), v. t. [imp. & p. p. Alleged
   (-l[e^]jd"); p. pr. & vb. n. Alleging.] [OE. aleggen to
   bring forward as evidence, OF. esligier to buy, prop. to free
   from legal difficulties, fr. an assumed LL. exlitigare; L. ex
   + litigare to quarrel, sue (see Litigate). The word was
   confused with L. allegare (see Allegation), and lex law.
   Cf. Allay.]
   1. To bring forward with positiveness; to declare; to affirm;
      to assert; as, to allege a fact.
      [1913 Webster]

   2. To cite or quote; as, to allege the authority of a judge.
      [Archaic]
      [1913 Webster]

   3. To produce or urge as a reason, plea, or excuse; as, he
      refused to lend, alleging a resolution against lending.
      [1913 Webster]

   Syn: To bring forward; adduce; advance; assign; produce;
        declare; affirm; assert; aver; predicate.
        [1913 Webster]

WordNet (r) 3.0 (2006):

alleged
    adj 1: declared but not proved; "alleged abuses of housing
           benefits"- Wall Street Journal
    2: doubtful or suspect; "these so-called experts are no help"
       [syn: alleged(a), so-called, supposed]

Moby Thesaurus II by Grady Ward, 1.0:

86 Moby Thesaurus words for "alleged":
   accountable, accounted as, affirmed, announced, ascribable,
   asserted, asseverated, assignable, assumed, assumptive, attested,
   attributable, attributed, averred, avouched, avowed, certified,
   charged, claimed, compare, conjectural, conjectured, credible,
   credited, declared, deemed, deposed, derivable from, derivational,
   derivative, described, designated, doubtful, dubious, due,
   enunciated, explicable, given, granted, hypocritical, hypothetical,
   imputable, imputed, in name only, inferred, manifestoed,
   ostensible, owing, plausible, pledged, postulated, postulational,
   predicated, premised, presumed, presumptive, pretended, pretexted,
   professed, pronounced, purported, putative, questionable,
   referable, referred to, reputed, self-styled, so-called,
   soi-disant, specious, stated, supposed, suppositional,
   supposititious, suppositive, suspected, sworn, sworn to,
   taken for granted, traceable, understood, vouched, vouched for,
   vowed, warranted, would-be