Mastered rhymes with:
astred, bastard, plastered, administered, astred, bastard, blistered, bolstered, bustard, cloistered, clustered, custard, festered, filibustered, flustered, fostered, mustard, mustered, pestered, plastered, registered, sequestered, unregistered, upholstered
Mastered sounds like:
magistrate, mainstreet, meckstroth, menstruate, mistreat, mistreated, mistretta, mostaert, mustard, mustered