improperus
Could not find inproperiorum in Logeion dictionaries.
inproperiorum Adjective: genitive plural comparative of improperus
inproperiorum Noun: neuter genitive plural of improperium
imprŏpĕrus (inpr-), a, um, adj. [2. in-properus],
- not hasting, slow: sorores, Sil. 3, 96.
improperus, a, um (in u. properus), langsam, zögernd, Sil. 3, 96.
imprŏpĕrus, a, um, qui ne se hâte pas : Sil. 3, 96.