ADJECTIVE (3)

1. able to exist and perform in harmonious or agreeable combination;
- Example: "a compatible married couple"
- Example: "her deeds were compatible with her ideology"

2. capable of being used with or connected to other devices or components without modification;

3. capable of forming a homogeneous mixture that neither separates nor is altered by chemical interaction;

The Collaborative International Dictionary of English v.0.48:

Compatible \Com*pat"i*ble\, a. [F., fr. LL.compatibilis, fr. L.
   compati. See Compassion.]
   Capable of existing in harmony; congruous; suitable; not
   repugnant; -- usually followed by with.
   [1913 Webster]

         Our poets have joined together such qualities as are by
         nature the most compatible.              --Broome.

   Syn: Consistent; suitable; agreeable; accordant.
        [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

123 Moby Thesaurus words for "compatible":
   accordant, affable, affirmative, agreeable, agreeing, akin,
   amiable, amicable, answerable, appropriate, at one, attuned,
   blissful, cheerful, civil, clubbable, clubbish, clubby, coexistent,
   coexisting, coherent, coincident, coinciding, commensurate,
   communicative, companionable, companionate, complaisant,
   concordant, concurring, conformable, congenial, congruent,
   congruous, consentaneous, consentient, consistent, consonant,
   cooperating, cooperative, cordial, correspondent, corresponding,
   courteous, desirable, dulcet, empathetic, empathic, en rapport,
   enjoyable, equivalent, fair, fair and pleasant, felicific,
   felicitous, fine, fit, fit for society, fitting, fond of society,
   frictionless, friendly, genial, good, goodly, gracious, grateful,
   gratifying, gregarious, harmonious, heart-warming, honeyed,
   hospitable, in accord, in agreement, in concert, in rapport,
   in sync, in synchronization, in tune, inaccordance, inharmony,
   likable, like-minded, meet, mellifluous, mellow, nice, of a piece,
   of like mind, of one mind, on all fours, peaceful, pleasant,
   pleasing, pleasurable, pleasure-giving, pleasureful, positive,
   proper, proportionate, reconcilable, rewarding, satisfying,
   self-consistent, sociable, social, social-minded, suitable, sweet,
   symbiotic, sympathetic, synchronized, synchronous, together,
   unanimous, understanding, uniform, unisonant, unisonous, united,
   urbane, welcome