What is "impersonal verb"

Impersonal \Im*per"son*al\, a. [L. impersonalis; pref. im- not + personalis personal: cf. F. impersonnel. See Personal.] Not personal; not representing a person; not having personality.

An almighty but impersonal power, called Fate.
--Sir J. Stephen.

Impersonal verb (Gram.), a verb used with an indeterminate subject, commonly, in English, with the impersonal pronoun it; as, it rains; it snows; methinks (it seems to me). Many verbs which are not strictly impersonal are often used impersonally; as, it goes well with him.

n. (context linguistics English) A verb used only in the infinitive or in the third-person. In the third person, the subject is either implied or a dummy.

In linguistics, an impersonal verb is one that has no determinate subject. For example, in the sentence "It rains", rain is an impersonal verb and the pronoun it does not refer to anything. In many languages the verb takes a third person singular inflection and often appears with an expletive subject. In the active voice, impersonal verbs can be used to express operation of nature, mental distress, and acts with no reference to the do-er. Impersonal verbs are also called weather verbs because they frequently appear in the context of weather description.