Here's what rhymes with serendipitiously.
speciously facetiously Words that almost rhyme with serendipitiously
grievously zealously cheekily deity legally speedily appreciably illegally ceaselessly ingeniously needlessly peaceably dreamily genially heedlessly piquancy seamlessly drearily egregiously peony reapply regally speechlessly piquantly secrecy decency peacefully decently fealty greedily regency ideality realty serenely unspeakably sleepily irredeemably obscenely breezily dubiety feasibly covetously heedfully inappreciably needfully sleeplessly sneakily creakily creepily wheezily anemically creamily recently obesity agreeably supremely uneasily unequally unevenly aridity gleefully indecency leniency unbelievably leniently deceitfully indecently heterogeneously phonemically believably greasily indefeasibly queasily coequally squeakily sleazily frequency frequently heterogeneity coherently irretrievably benignity disagreeably naivety congenially centripetally conceitedly unrelievedly infrequently conceivably unfrequently infrequency conveniently homogeneity spontaneity historicity crystallinity simultaneity contemporaneity inconceivably inconveniently