Passively rhymes with:
impassively, impassively, massively, aggressively, cohesively, comprehensively, compulsively, conclusively, decisively, defensively, derisively, effusively, excessively, exclusively, expensively, explosively, extensively, impassively, impressively, impulsively, inconclusively, inexpensively, intensively, massively, obsessively, offensively, persuasively, progressively, reflexively, successively
Passively sounds like:
passable, passably, peaceable, peaceably, peaceful, peacefully, possible, possibly, psychobabble