Correct spelling for the English word "isobrious" is [a͡ɪsˈɒbɹɪəs], [aɪsˈɒbɹɪəs], [aɪ_s_ˈɒ_b_ɹ_ɪ__ə_s] (IPA phonetic alphabet).
In bot., applied to the dicotyledons, because both seem to be developed with equal force.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.