The Collaborative International Dictionary of English v.0.48:

Verifiable \Ver"i*fi`a*ble\, a.
   Capable of being verified; confirmable. --Bp. Hall.
   [1913 Webster]

WordNet (r) 3.0 (2006):

verifiable
    adj 1: capable of being verified; "a verifiable account of the
           incident"
    2: capable of being tested (verified or falsified) by experiment
       or observation [syn: confirmable, verifiable,
       falsifiable]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "verifiable":
   absolute, actual, admitting no question, apodictic, attestable,
   authenticatable, checkable, confirmable, demonstrable,
   demonstratable, evincible, factual, historical, inappealable,
   incontestable, incontrovertible, indisputable, indubitable,
   irrefragable, irrefutable, provable, real, self-evident,
   substantiatable, supportable, sustainable, testable, unanswerable,
   unconfutable, undeniable, unimpeachable, unquestionable,
   unrefutable, validatable