Lewis & Short

impersōnālis (inp-), e, adj. [2. inpersonalis], impersonal: verba, in grammar, Charis. 2 and 3; Diom. 1 et saep.
Adv.: impersōnālĭter, impersonally: sive impersonaliter dari servus meus stipuletur, i. e. without naming the person, Dig. 45, 3, 15.
Gramm. t. t., Macr. de Diff. 20, 3.