The Collaborative International Dictionary of English v.0.48:

Detectable \De*tect"a*ble\ (-[.a]*b'l), Detectible
\De*tect"i*ble\, a.
   Capable of being detected or found out; as, parties not
   detectable. "Errors detectible at a glance." --Latham.
   [1913 Webster]

WordNet (r) 3.0 (2006):

detectable
    adj 1: capable of being detected; "after a noticeable pause the
           lecturer continued" [syn: detectable, noticeable]
    2: easily seen or detected; "a detectable note of sarcasm"; "he
       continued after a perceptible pause" [syn: detectable,
       perceptible]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "detectable":
   apparent, appreciable, beholdable, determinable, discernible,
   disclosable, disclosed, discoverable, evident, exposable, exposed,
   exposed to view, findable, hanging out, hot, in evidence,
   in full view, in plain sight, in view, insight, manifest, naked,
   noticeable, observable, open, open to view, outcropping, palpable,
   perceivable, perceptible, recognizable, revealed, seeable,
   sensible, showing, spottable, tangible, to be seen, unclouded,
   unconcealed, undisguised, unhidden, viewable, visible, visual,
   warm, witnessable