The Collaborative International Dictionary of English v.0.48:

Indeterminate \In`de*ter"mi*nate\, a. [L. indeterminatus.]
   Not determinate; not certain or fixed; indefinite; not
   precise; as, an indeterminate number of years. --Paley.
   [1913 Webster]

   Indeterminate analysis (Math.), that branch of analysis
      which has for its object the solution of indeterminate
      problems.

   Indeterminate coefficients (Math.), coefficients
      arbitrarily assumed for convenience of calculation, or to
      facilitate some artifice of analysis. Their values are
      subsequently determined.

   Indeterminate equation (Math.), an equation in which the
      unknown quantities admit of an infinite number of values,
      or sets of values. A group of equations is indeterminate
      when it contains more unknown quantities than there are
      equations.

   Indeterminate inflorescence (Bot.), a mode of inflorescence
      in which the flowers all arise from axillary buds, the
      terminal bud going on to grow and sometimes continuing the
      stem indefinitely; -- called also acropetal
      inflorescence, botryose inflorescence, centripetal
      inflorescence, and indefinite inflorescence. --Gray.

   Indeterminate problem (Math.), a problem which admits of an
      infinite number of solutions, or one in which there are
      fewer imposed conditions than there are unknown or
      required results.

   Indeterminate quantity (Math.), a quantity which has no
      fixed value, but which may be varied in accordance with
      any proposed condition.

   Indeterminate series (Math.), a series whose terms proceed
      by the powers of an indeterminate quantity, sometimes also
      with indeterminate exponents, or indeterminate
      coefficients. -- In`de*ter"mi*nate*ly adv. --
      In`de*ter"mi*nate*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

indeterminate
    adj 1: not precisely determined or established; not fixed or
           known in advance; "of indeterminate age"; "a zillion is a
           large indeterminate number"; "an indeterminate point of
           law"; "the influence of environment is indeterminate";
           "an indeterminate future" [syn: indeterminate,
           undetermined] [ant: determinate]
    2: having a capacity for continuing to grow at the apex; "an
       indeterminate stem" [ant: determinate]
    3: of uncertain or ambiguous nature; "the equivocal (or
       indeterminate) objects painted by surrealists"
    4: not capable of being determined; "the indeterminate number of
       plant species in the jungle"
    5: not leading to a definite ending or result; "an indeterminate
       campaign"

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "indeterminate":
   abstract, accidental, adventitious, aleatoric, aleatory, amorphic,
   amorphous, anarchic, baggy, bland, blind, blobby, blurred, blurry,
   broad, casual, causeless, chance, chancy, chaotic, characterless,
   clear as mud, cloudy, collective, confused, contingent, dark,
   destinal, dicey, dim, disordered, disorderly, fatal, fatidic,
   featureless, fluky, foggy, formless, fortuitous, fuzzy, general,
   generalized, generic, hazy, hit-or-miss, iffy, ill-defined,
   imprecise, inaccurate, inchoate, incidental, incoherent,
   indecisive, indefinable, indefinite, indeterminable, indistinct,
   inexact, inform, kaleidoscopic, lax, loose, lumpen, misty, muddy,
   murky, nebulous, neutral, nondescript, nonspecific, obscure,
   opaque, orderless, random, risky, shadowed forth, shadowy,
   shapeless, stochastic, sweeping, transcendent, uncaused,
   uncharacterized, unclear, undefined, undestined, undetermined,
   undifferentiated, unexpected, unforeseeable, unforeseen,
   unlooked-for, unordered, unorganized, unplain, unpredictable,
   unspecified, vague, veiled, wide



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

INDETERMINATE. That which is uncertain or not particularly designated; as,
if I sell you one hundred bushels of wheat, without stating what wheat. 1
Bouv. Inst. n. 950.