The Collaborative International Dictionary of English v.0.48:

Ionic \I*on"ic\, n.
   1. (Pros.)
      (a) A foot consisting of four syllables: either two long
          and two short, -- that is, a spondee and a pyrrhic, in
          which case it is called the greater Ionic; or two
          short and two long, -- that is, a pyrrhic and a
          spondee, in which case it is called the smaller
          Ionic.
      (b) A verse or meter composed or consisting of Ionic feet.
          [1913 Webster]

   2. The Ionic dialect; as, the Homeric Ionic.
      [1913 Webster]

   3. (Print.) Ionic type.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ionic \I*on"ic\, a. [L. Ionicus, Gr. ?, fr. ? Ionia.]
   [1913 Webster]
   1. Of or pertaining to Ionia or the Ionians.
      [1913 Webster]

   2. (Arch.) Pertaining to the Ionic order of architecture, one
      of the three orders invented by the Greeks, and one of the
      five recognized by the Italian writers of the sixteenth
      century. Its distinguishing feature is a capital with
      spiral volutes. See Illust. of Capital.
      [1913 Webster]

   Ionic dialect (Gr. Gram.), a dialect of the Greek language,
      used in Ionia. The Homeric poems are written in what is
      designated old Ionic, as distinguished from new Ionic, or
      Attic, the dialect of all cultivated Greeks in the period
      of Athenian prosperity and glory.

   Ionic foot. (Pros.) See Ionic, n., 1.

   Ionic mode, or Ionian mode, (Mus.), an ancient mode,
      supposed to correspond with the modern major scale of C.


   Ionic sect, a sect of philosophers founded by Thales of
      Miletus, in Ionia. Their distinguishing tenet was, that
      water is the original principle of all things.

   Ionic type, a kind of heavy-faced type (as that of the
      following line).
      [1913 Webster]

   Note: This is Nonpareil Ionic.

The Collaborative International Dictionary of English v.0.48:

ionic \i*on"ic\ a. (Chem.)
   Of or pertaining to ions; composed of ions, containing ions,
   or breaking down into ions when dissolved in a polar solvent;
   as, an ionic solution will conduct a current of electricity.
   Opposite of nonionic.
   [PJC]

WordNet (r) 3.0 (2006):

ionic
    adj 1: containing or involving or occurring in the form of ions;
           "ionic charge"; "ionic crystals"; "ionic hydrogen" [ant:
           nonionic, nonpolar]
    2: of or pertaining to the Ionic order of classical Greek
       architecture
    3: of or relating to Ionia or its inhabitants or its language
    n 1: the dialect of Ancient Greek spoken and written in Attica
         and Athens and Ionia [syn: Attic, Ionic, Ionic
         dialect, Classical Greek]