The Collaborative International Dictionary of English v.0.48:

Ratable \Rat"a*ble\ (r[=a]t"[.a]*b'l), a.
   1. Capable of being rated, or set at a certain value.
      [1913 Webster]

            Twenty orae were ratable to [at] two marks of
            silver.                               --Camden.
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   2. Liable to, or subjected by law to, taxation; as, ratable
      estate.
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   3. Made at a proportionate rate; as, ratable payments. --
      Rat"a*ble*ness, n. -- Rat"a*bly, adv.
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