Correct spelling for the English word "Prepositure" is [pɹˈɛpəsˌɪt͡ʃə], [pɹˈɛpəsˌɪtʃə], [p_ɹ_ˈɛ_p_ə_s_ˌɪ_tʃ_ə] (IPA phonetic alphabet).
A provostship.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.