The Collaborative International Dictionary of English v.0.48:

Innuendo \In`nu*en"do\, n.; pl. Innuedoes(?). [L., by
   intimation, by hinting, gerund of innuere, innutum, to give a
   nod, to intimate; pref. in- in, to + -nuere (in comp.) to
   nod. See Nutation.]
   1. An oblique hint; a remote allusion or reference, usually
      derogatory to a person or thing not named; an insinuation.
      [1913 Webster]

            Mercury . . . owns it a marriage by an innuendo.
                                                  --Dryden.
      [1913 Webster]

            Pursue your trade of scandal picking;
            Your innuendoes, when you tell us,
            That Stella loves to talk with fellows. --Swift.
      [1913 Webster]

   2. (Law) An averment employed in pleading, to point the
      application of matter otherwise unintelligible; an
      interpretative parenthesis thrown into quoted matter to
      explain an obscure word or words; -- as, the plaintiff
      avers that the defendant said that he (innuendo the
      plaintiff) was a thief. --Wharton.
      [1913 Webster]

   Note: The term is so applied from having been the
         introductory word of this averment or parenthetic
         explanation when pleadings were in Latin. The word
         "meaning" is used as its equivalent in modern forms.

   Syn: Insinuation; suggestion; hint; intimation; reference;
        allusion; implication; representation; -- Innuendo,
        Insinuation.

   Usage: An innuendo is an equivocal allusion so framed as to
          point distinctly at something which is injurious to
          the character or reputation of the person referred to.
          An insinuation turns on no such double use of
          language, but consists in artfully winding into the
          mind imputations of an injurious nature without making
          any direct charge.
          [1913 Webster]

WordNet (r) 3.0 (2006):

innuendo
    n 1: an indirect (and usually malicious) implication [syn:
         insinuation, innuendo]

Moby Thesaurus II by Grady Ward, 1.0:

104 Moby Thesaurus words for "innuendo":
   accusal, accusation, accusing, allegation, allegement, allegory,
   allusion, animadversion, arcane meaning, arraignment, aspersion,
   assumption, bill of particulars, blame, bringing of charges,
   bringing to book, broad hint, causticity, charge, clue, coloration,
   complaint, connotation, count, cue, cynicism, delation,
   denouncement, denunciation, gentle hint, gesture, glimmer,
   glimmering, hint, impeachment, implication, implied meaning,
   import, imputation, index, indication, indictment, indirect,
   inference, information, inkling, insinuation, intimation,
   invective, ironic suggestion, irony, kick, lawsuit,
   laying of charges, look, meaning, metaphorical sense, nod, nuance,
   nudge, occult meaning, overtone, personal remark, personality,
   plaint, presumption, presupposition, prompt, prosecution,
   reference, reflection, reproach, sarcasm, satire, satiric wit,
   scent, sign, signal, slur, sly suggestion, spoor, subsense,
   subsidiary sense, suggestion, suit, supposition, suspicion,
   symbolism, symptom, taxing, telltale, tinge, touch, track,
   true bill, uncomplimentary remark, undercurrent, undermeaning,
   undertone, unspoken accusation, veiled accusation, whisper,
   whispering campaign, wink



Bouvier's Law Dictionary, Revised 6th Ed (1856):

INNUENDO, pleading. An averment which explains the defendant's meaning by
reference to antecedent matter. Salk. 513; 1 Ld. Raym. 256; 12 Mod. 139; 1
Saund. 243. The innuendo is mostly used in actions for slander. An innuendo,
as, "he the said plaintiff meaning," is only explanatory of some matter
expressed; it serves to apply the slander to the precedent matter, but
cannot add or enlarge, extend, or change the sense of the previous words,
and the matter to which it alludes must always appear from the antecedent
parts of the declaration or indictment. 1 Chit. Pl. 383; 3 Caines' Rep. 76;
7 Johns. R. 271; 5 Johns. R. 211; 8 Johns. R. 109; 8 N. H. Rep. 256.
     3. It is necessary only when the intent may be mistaken, or when it
cannot be collected from the libel or slander itself. Cowp. 679; 5 East,
463.
     4. If the innuendo materially enlarge the sense of the words it will
vitiate the declaration or indictment. 6 T. R. 691; 5 Binn. 218; 5 Johns. R.
220; 6 Johns. R. 83; 7 Johns. Rep. 271. But when the new matter stated in an
innuendo is not necessary to support the action, it may be rejected as
surplusage. 9 East, R. 95; 7 Johns. R. 272. Vide, generally, Stark. on Slan.
293; 1 Chit. Pl. 383; 3 Chit. Cr. Law, 873; Bac. Ab. Slander, R; 1 Saund.
243, n. 4; 4 Com. Dig. 712; 14 Vin. Ab. 442; Dane's Ab. Index, h. t.; 4 Co.
17.