Theoretically rhymes with:
hermetically, magnetically, parenthetically, pathetically, sympathetically, critically, fanatically, hermetically, journalistically, magnetically, majestically, mathematically, optimistically, parenthetically, pathetically, politically, pragmatically, ritualistically, romantically, skeptically, statistically, sympathetically, tactically, therapeutically, uncritically
Theoretically sounds like:
tartaglia, theoretical, threadgill