Here's what rhymes with definable.
indefinable undefinable Words that almost rhyme with definable
desirable viable sizable sizeable decidable liable excitable assignable likable likeable risible liveable deniable reliable advisable undesirable pliable describable survivable undeniable inadvisable indictable ascribable recyclable certifiable notifiable climbable unlikeable unliveable justifiable unreliable indescribable verifiable libidinal realizable cognizable maniacal analyzable rectifiable nonassignable identifiable irreconcilable unjustifiable ammoniacal classifiable demoniacal reconcilable unverifiable recognizable unidentifiable unrecognizable monomaniacal