Unbuilt rhymes with:
bildt, built, overbuilt, rebuilt, welbilt, bildt, built, gilt, guilt, hilt, jilt, kilt, lilt, milt, overbuilt, quilt, rebuilt, schildt, schilt, silt, spilt, stilt, tilt, welbilt, wildt, wilt
Unbuilt sounds like:
umfleet, umphlett, unaffiliate, unaffiliated, unbolt, unbolted, unemployed, unfilled, unfold, unfolded, unveiled