Mediocre rhymes with:
boecker, boeker, boker, bokor, bowker, broecker, broeker, broker, coker, croaker, croker, exbroker, folker, hoecker, joker, kocur, koker, kolker, kroeker, loker, noecker, nonsmoker, ochre, poker, rapoca, roecker, schmoker, smoker, soaker, stoecker, stoker, zocor
Mediocre sounds like:
madagascar, matscher, matsuura, medgar, medicare, mediscare, medsker, mentzer, metsker, metzer, metzgar, metzger, metzker, mintzer, mitsuru, montazeri, montessori, motzer