Untrue rhymes with:
construe, misconstrue, strew, treu, trew, trieu, true, abreu, accrue, aeroperu, brew, brue, construe, crew, crewe, drew, drive-thru, dru, fauroux, frew, frueh, giroux, grew, grewe, marrou, mcgrew, misconstrue, outgrew, overthrew, prew, pru, prue, prugh, rew, rhew, rhue, rioux, roux, ru, rue, screw, strew, threw, through, thru, treu, trew, trieu, true, withdrew
Untrue sounds like:
under, underway, underwear, unitary