The Collaborative International Dictionary of English v.0.48:

Measurable \Meas"ur*a*ble\, a. [F. mesurable, L. mensurabilis.
   See Measure, and cf. Mensurable.]
   [1913 Webster]
   1. Capable of being measured; susceptible of mensuration or
      computation.
      [1913 Webster]

   2. Moderate; temperate; not excessive.
      [1913 Webster]

            Of his diet measurable was he.        --Chaucer.
      [1913 Webster] -- Meas"ur*a*ble*ness, n. --
      Meas"ur*a*bly, adv.
      [1913 Webster]

            Yet do it measurably, as it becometh Christians.
                                                  --Latimer.
      [1913 Webster]

WordNet (r) 3.0 (2006):

measurable
    adj 1: capable of being measured; "measurable depths" [syn:
           measurable, mensurable] [ant: immeasurable,
           immensurable, unmeasurable, unmeasured]
    2: of distinguished importance; "a measurable figure in
       literature"

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "measurable":
   appraisable, appreciable, assessable, calculable, computable,
   countable, determinable, estimable, fathomable, gaugeable,
   mensurable, meterable, noticeable, numberable, numerable,
   perceptible, quantifiable, quantizable, reckonable