Untenable rhymes with:
tenable, amenable, tenable, venable, abominable, actionable, amenable, anable, annabelle, annable, attainable, burnable, cannibal, combinable, conable, definable, determinable, discernible, explainable, fashionable, fissionable, imaginable, impregnable, impressionable, inalienable, indefinable, interminable, objectionable, obtainable, personable, questionable, reasonable, returnable, seasonable, sustainable, tenable, terminable, trainable, tunable, unalienable, unattainable, unconscionable, unexplainable, unfashionable, ungovernable, unimaginable, unmentionable, unobtainable, unquestionable, unreasonable, unsustainable, unwinnable, venable, winnable
Untenable sounds like:
unattainable, undeniable, undeniably, unmentionable