The Collaborative International Dictionary of English v.0.48:

Promiscuous \Pro*mis"cu*ous\, a. [L. promiscuus; pro before, in
   place of, for + miscere to mix. See Mix. ]
   [1913 Webster]
   1. Consisting of individuals united in a body or mass without
      order; mingled; confused; undistinguished; as, a
      promiscuous crowd or mass.
      [1913 Webster]

            A wild, where weeds and flowers promiscuous shoot.
                                                  --Pope.
      [1913 Webster]

   2. Distributed or applied without order or discrimination;
      not restricted to an individual; common; indiscriminate;
      as, promiscuous love or intercourse.
      [1913 Webster]

WordNet (r) 3.0 (2006):

promiscuous
    adj 1: not selective of a single class or person; "Clinton was
           criticized for his promiscuous solicitation of campaign
           money"
    2: casual and unrestrained in sexual behavior; "her easy
       virtue"; "he was told to avoid loose (or light) women";
       "wanton behavior" [syn: easy, light, loose,
       promiscuous, sluttish, wanton]

Moby Thesaurus II by Grady Ward, 1.0:

197 Moby Thesaurus words for "promiscuous":
   Paphian, abandoned, aimless, amalgamated, ambiguous, ambivalent,
   amoral, amorphous, amphibious, assorted, blanket, blended, botched,
   bungling, capricious, careless, casual, causeless, chambering,
   chaotic, clumsy, combined, complex, composite, compound,
   compounded, confused, conglomerate, cursory, dappled, debauched,
   deficient, depraved, designless, desultory, disarticulated,
   discontinuous, dishonorable, disjunct, disordered, disorderly,
   disorganized, dispersed, disproportionate, disregardful,
   dissipated, dissolute, driftless, dysteleological, easy, eclectic,
   equivocal, erratic, faithless, fast, fifty-fifty, fitful, formless,
   frivolous, general, gratuitous, half-and-half, half-assed,
   haphazard, heedless, helter-skelter, heterogeneous,
   higgledy-piggledy, hit-and-miss, hit-or-miss, immethodical,
   immoderate, immoral, imprudent, inchoate, incoherent, indecent,
   indifferent, indiscreet, indiscriminate, indiscriminative,
   inexplicable, insensitive, intermingled, intermixed, intricate,
   ironic, irregular, irresponsible, jumbled, lax, libertine,
   licentious, light, loose, loose-moraled, many-sided, meaningless,
   medley, messy, mindless, mingled, miscellaneous, misshapen, mixed,
   motley, multifaceted, multifarious, multinational, multiracial,
   neglectful, negligent, nonjudgmental, nonsymmetrical,
   nonsystematic, nonuniform, of easy virtue, of loose morals,
   orderless, patchy, perfunctory, planless, pluralistic, profligate,
   purposeless, random, scrambled, senseless, shapeless, slack,
   slipshod, slipshoddy, sloppy, slovenly, sluttish, spasmodic,
   sporadic, stochastic, straggling, straggly, stray, syncretic,
   systemless, tactless, thoughtless, thrown together, unaccountable,
   unarranged, unbridled, uncaring, unchaste, unclassified,
   unconscientious, unconsidered, uncontrolled, uncritical,
   uncriticizing, uncurbed, undemanding, undifferentiating,
   undirected, undiscreet, undiscriminating, undiscriminative,
   unexacting, unfaithful, unfastidious, unfussy, ungoverned,
   ungraded, uninhibited, unjoined, unmethodical, unmeticulous,
   unmotivated, unordered, unorganized, unparticular, unplanned,
   unrestrained, unselective, unsorted, unsubtle, unsymmetrical,
   unsystematic, untactful, unthinking, untidy, ununiform, vague,
   varied, wandering, wanton, wayward, wholesale, whorish, wild