Retrain rhymes with:
constrain, overtrain, restrain, strain, train, trane, bahrain, brain, constrain, crain, craine, crane, crayne, dahrain, decrane, defrain, drain, draine, drane, dufrane, frain, fraine, frane, frayn, frayne, frein, freyne, grain, grein, krain, krane, krein, mcgrain, mcgrane, overtrain, rain, raine, rayne, refrain, reign, rein, reine, restrain, sprain, strain, tirane, train, trane, ukraine, vrain
Retrain sounds like:
ratterman, readerman, redrawn, return, returnee, ruderman