Unambiguous rhymes with:
tenuous, fatuous, presumptuous, sensuous, tenuous, tortuous, voluptuous, assiduous, fatuous, impetuous, incestuous, inconspicuous, marquess, presumptuous, promiscuous, sensuous, sinuous, sumptuous, tenuous, tortuous, unctuous, voluptuous
Unambiguous sounds like:
umbach, umbaugh, unbook, univisa, unpack