The Collaborative International Dictionary of English v.0.48:

Miscible \Mis"ci*ble\, a. [Cf. F. miscible, fr. L. miscere to
   mix.]
   Capable of being mixed; mixable. --Burke.
   [1913 Webster]

   2. (Chem.) Mixable in all proportions; forming a single phase
      when mixed in any proportion; -- of liquids; as, water and
      alcohol are miscible in all proportions; water and
      gasoline are not miscible; benzene and ethyl alcohol are
      miscible, and ethyl alcohol is miscible with water, but
      water is not miscible with benzene..
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

miscible
    adj 1: (chemistry, physics) capable of being mixed [syn:
           miscible, mixable] [ant: immiscible, non-
           miscible, unmixable]