Mumbled rhymes with:
crumbled, fumbled, grumbled, humbled, jumbled, rumbled, stumbled, tumbled, ambled, assembled, crumbled, disassembled, fumbled, gambled, grumbled, humbled, jumbled, rambled, reassembled, resembled, rumbled, scrambled, stumbled, trembled, tumbled
Mumbled sounds like:
manifold, manipulate, manipulated, maplewood, mayfield, minefield, minnifield, mobility, mofield, muffled, muffoletto