The Collaborative International Dictionary of English v.0.48:

Consistent \Con*sist"ent\, a. [L. consistens, p. pr.: cf. F.
   consistant.]
   1. Possessing firmness or fixedness; firm; hard; solid.
      [1913 Webster]

            The humoral and consistent parts of the body.
                                                  --Harvey.
      [1913 Webster]

   2. Having agreement with itself or with something else;
      having harmony among its parts; possesing unity;
      accordant; harmonious; congruous; compatible; uniform; not
      contradictory.
      [1913 Webster]

            Show me one that has it in his power
            To act consistent with himself an hour. --Pope.
      [1913 Webster]

            With reference to such a lord, to serve and to be
            free are terms not consistent only, but equivalent.
                                                  --South.
      [1913 Webster]

   3. Living or acting in conformity with one's belief or
      professions.
      [1913 Webster]

            It was utterly to be at once a consistent Quaker and
            a conspirator.                        --Macaulay.
      [1913 Webster]

WordNet (r) 3.0 (2006):

consistent
    adj 1: (sometimes followed by `with') in agreement or consistent
           or reliable; "testimony consistent with the known facts";
           "I have decided that the course of conduct which I am
           following is consistent with my sense of responsibility
           as president in time of war"- FDR [ant: inconsistent]
    2: capable of being reproduced; "astonishingly reproducible
       results can be obtained" [syn: reproducible, consistent]
       [ant: irreproducible, unreproducible]
    3: marked by an orderly, logical, and aesthetically consistent
       relation of parts; "a coherent argument" [syn: coherent,
       consistent, logical, ordered] [ant: incoherent]
    4: the same throughout in structure or composition; "bituminous
       coal is often treated as a consistent and homogeneous
       product" [syn: consistent, uniform]

Moby Thesaurus II by Grady Ward, 1.0:

162 Moby Thesaurus words for "consistent":
   accordant, affirmative, agreeable, agreeing, alike, answerable,
   at one, authoritative, automatic, balanced, binding, clean-cut,
   clear, clear as crystal, clear as day, clear-cut, coexistent,
   coexisting, cogent, coherent, coincident, coinciding, commensurate,
   compatible, concordant, concurring, conformable, conforming,
   congenial, congruent, congruous, connected, consecutive,
   consentaneous, consentient, consonant, constant, continuous,
   cooperating, cooperative, correspondent, corresponding, crisp,
   crystal-clear, crystalline, defined, definite, dependable, devoted,
   direct, distinct, en rapport, equable, equal, equivalent, even,
   explicit, express, faithful, firm, flat, good, harmonious,
   homogeneous, immutable, in accord, in agreement, in harmony,
   in keeping, in rapport, in sync, in synchronization, inaccordance,
   inharmony, invariable, joined, just, lawful, legal, legitimate,
   level, like-minded, limpid, logical, loud and clear, loyal, lucid,
   luminous, marble-constant, measured, mechanical, methodic,
   monolithic, of a piece, of like mind, of one mind, on all fours,
   ordered, orderly, pellucid, persistent, perspicuous, plain,
   positive, predictable, proportionate, reconcilable, regular,
   robotlike, self-consistent, sequent, sequential, serial, simple,
   smooth, solid, sound, stable, staunch, steadfast, steady,
   straightforward, substantial, sufficient, symbiotic, sympathetic,
   synchronized, synchronous, systematic, tight, translucent,
   transparent, transpicuous, true, true-blue, unambiguous, unanimous,
   unbroken, unchangeable, unchanged, unchanging, unconfused,
   undeviating, undifferentiated, undiversified, unequivocal,
   unfailing, uniform, uninterrupted, unisonant, unisonous, univocal,
   unmistakable, unruffled, unswerving, unvaried, unvarying, valid,
   weighty, well-defined, well-founded, well-grounded



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

CONSISTENT. That which agrees with something else; as a consistent
condition, which is one which agrees with all other parts of a contract, or
which can be reconciled with every other part. 1 Bouv. Just. n. 752,