Irreversibly rhymes with:
flexibly, forcibly, impossibly, inadmissibly, inflexibly, irresponsibly, noticeably, ostensibly, passably, peaceably, possibly, responsibly, sensibly
flexibly, forcibly, impossibly, inadmissibly, inflexibly, irresponsibly, noticeably, ostensibly, passably, peaceably, possibly, responsibly, sensibly