in *Grammar*, a verb to which the nominative of any certain person cannot be prefixed; or, as others define it, a verb destitute of the two first and primary persons, as deet, aportet, &c., the impersonal verbs of the active voice end in t, and those of the passive in tur; they are conjugated through the third person singular of almost all the tenes and moods: they want the imperative, instead of which we use the present of the subjunctive; as punitetur, pugnetur, &c.; nor, but a few excepted, are they to be met with in the supines, participles or gerunds.

**IMPEVIOUS**, a thing not to be pervaded or passed through, either by reason of the closeness of its pores, or the particular configuration of its parts.

**IMPETIGO**, in *Medicine*, an extreme roughness and foulness of the skin, attended with an itching and plentiful scurf.

The impetigo is a species of dry pruriginous itch, wherein scales or scurf succeed apace; arising from saline corrosive humours thrown out upon the exterior parts of the body, by which means the internal parts are usually relieved.