Here's what rhymes with indistinguishable.

Consider these alternatives

unrecognizable / advisable unrecognisable / recognisable invulnerable / vulnerable identifiable / viable devoid / avoid irrelevant / relevant recognizable / advisable dissimilar / similar unidentifiable / viable distinguishable / indistinguishable commonplace / place phenotypically / typically unmodified / side morph / course undifferentiated / dated obsolete / feet superfluous / thus indecipherable / decipherable differentiate / state unintelligible / intelligible