The Collaborative International Dictionary of English v.0.48:

Noticeable \No"tice*a*ble\, a.
   Capable of being observed; worthy of notice; likely to
   attract observation; conspicuous.
   [1913 Webster]

         A noticeable man, with large gray eyes.  --Wordsworth.
   [1913 Webster]

WordNet (r) 3.0 (2006):

noticeable
    adj 1: capable or worthy of being perceived; "noticeable shadows
           under her eyes"; "noticeable for its vivid historical
           background"; "a noticeable lack of friendliness" [ant:
           unnoticeable]
    2: capable of being detected; "after a noticeable pause the
       lecturer continued" [syn: detectable, noticeable]
    3: undesirably noticeable; "the obtrusive behavior of a spoiled
       child"; "equally obtrusive was the graffiti" [syn:
       obtrusive, noticeable] [ant: unnoticeable,
       unobtrusive]
    4: readily noticed; "a noticeable resemblance"

Moby Thesaurus II by Grady Ward, 1.0:

127 Moby Thesaurus words for "noticeable":
   acquaint, advise, appalling, apparent, appraisable, appreciable,
   apprise, arrant, arresting, assessable, astonishing, beholdable,
   blatant, bold, calculable, clear, clear as crystal, clear-cut,
   clue, computable, considerable, conspicuous, crystal-clear,
   detectable, determinable, discernible, disclosed, distinct,
   distinguishable, egregious, especial, estimable, evident,
   exceptional, explicit, exposed, exposed to view, express,
   extraordinary, eye-catching, fabulous, fantastic, fathomable,
   flagrant, formidable, gaugeable, glaring, hanging out, important,
   in evidence, in full view, in plain sight, in relief,
   in the foreground, in view, incredible, indisputable, indubitable,
   insight, major, manifest, marked, marvelous, measurable,
   mensurable, meterable, naked, notable, noteworthy, notify,
   notorious, numerable, observable, obtrusive, obvious, of mark,
   open, open to view, open-and-shut, ostensible, outcropping,
   outstanding, palpable, patent, perceivable, perceptible,
   perspicuous, plain, plain as day, pointed, prominent, pronounced,
   quantifiable, quantizable, recognizable, remarkable, reveal,
   revealed, salient, seeable, self-evident, self-explaining,
   self-explanatory, sensational, showing, signal, significant,
   singular, spectacular, staring, stark-staring, sticking out,
   striking, superior, tangible, to be seen, unclouded, uncommon,
   unconcealed, undisguised, unhidden, unmistakable, viewable,
   visible, visual, witnessable, wonderful