Rationally rhymes with:
irrationally, internationally, irrationally, nationally, additionally, conditionally, congressionally, constitutionally, conventionally, educationally, exceptionally, fractionally, functionally, generationally, institutionally, intentionally, internationally, irrationally, nationally, nutritionally, operationally, professionally, proportionally, rotationally, traditionally, unconditionally, unconstitutionally, unintentionally
Rationally sounds like:
radmilla, rational, rationale, retinal, retinol, retinyl, rotational, rotationally, routinely