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):

measurably
    adv 1: to a measurable degree; "the difference is measurably
           large" [ant: immeasurably]