reversionary UK /ɹɪˈvɜː(ɹ)ʒənəɹi/US /ɹəˈvɝʒəˌnɛɹi/adjective 1noun 1forms 3 adjective1 •Pertaining to reversion, especially that of an estate.Small animals Began to mooch around and climb up this Reversionary desk and dustable heirloom. — 1958 noun1 •A reversioner. formsreversionaries · more reversionary · most reversionary