Preexisting rhymes with:
coexisting, existing, coexisting, existing, coexisting, existing, resisting, assisting, coexisting, consisting, delisting, enlisting, existing, insisting, listing, persisting, resisting, thristing, twisting
Preexisting sounds like:
parachuting, percutaneous, persecuting, persecutions, persistence, persisting, persuading, precautions, precedence, preceding, preceeding, presidencies, presidency, presidency's, presiding, preston's, proceeding, proceedings, projecting, projections, prosecuting, prosecution's, prosecutions